Classification and marking of motor oil on SAE viscosity. HTHS - High-temperature viscosity on shear Butter lump stabilizers

When choosing a motor oil for winter operating You should pay attention to the following specificationswhich manufacturers lubricants Usually indicate technical descriptions.

1. Frozening temperature (yield loss) or Pour Point.It is measured according to GOST 20287 or DIN ISO 3016 or ASTM D97. This parameter does not have a special physical meaning to operate the engine. It is indicated for the purpose of storing the oil and indicates that the oil can be pouring from one container to another. Especially since there are special additives - depressors that reduce the freezing temperature of mineral oils. Adding a large number of depressor additives to mineral hydrocracking basic oil You can achieve the freezing temperature of the finished oil, even below minus 40 C.

2. Dynamic viscosityat low temperature measured using a cold engine start imitator CCS (COLD CRANKING SIMULATOR) According to DIN 51 377 or ASTM D 2602 methods. This important parameter Shows how much the engine will be difficult to turn cold oil in the cylinder-piston group. Measured in MPa * p. The lower this parameter, the better. Boundary viscosity values \u200b\u200bfor different classes Oils determines the international SAE J300 standard.

SAE J300 Standard Last Editorial

3. Dynamic viscosity at low temperature measured on minimizing viscose MRV (Mini Rotary Viscometer). It is measured at a temperature of 5 s below than CCS and is also called the "pumping viscosity". This indicator indicates whether the thickened oil will be able to pump the engine oil pump and at what speed the cold oil will be fed by maslochanals to the lubricant points. Measured in MPa * p. All three parameters are the freezing temperature, the dynamic viscosity of CCS and the dynamic viscosity of the MRV, the less, the better. CCS and MRV parameters are involved in determining the SAE viscosity class. The SAE standard determines fade viscosity values \u200b\u200bat certain temperatures. For example, oil viscosity 5W-XX (20, 30, 40, 50) should not have the viscosity of CCS for minus 30 c more than 6600, and the mRV viscosity should not be greater than 60000. Then this oil has the right to be marked as 5W- XX.

In domestic conditions, it is also possible to estimate low-temperature properties using various devices. And if for many regions of Russia frosts under 40 with this is a rarity, then for Yakutia it is weekdays. Here is an example of such tests from Drävovchanina Andrei Tuskina Aka Belkovodus.

Generally accepted technical fact - Oils made on the basis of polyalphaolefins (PJSC) have the best low-temperature properties compared to mineral hydrocracking oils. At the same time, the oils on the PJSC have explicit advantages and at summer exploitation: lower evaporation - the NoOck parameter in those. Descriptions, higher thermal stability, low oxidation and coking, the best heat dissipation from lubricated surfaces.

The most important operational properties motor oils These are: viscosity-temperature (viscosity, viscosity index, frosted temperature), anti-wear, antioxidant, dispersing (detergents), corrosion, etc.

Viscosity of temperature properties.The viscosity and its temperature dependence are the most important indicator of the quality of motor oils.

The ability to provide liquid, hydrodynamic friction in bearings, and, consequently, their normal operation depends on the viscosity of the oil. The viscosity of the oil affects the wear of the neck of the crankshaft and the liners of the bearings. From the viscosity of the oil depends the number of heat friction venge. The less viscosity, the better the bearing is cooled, since it pumps more oil through it, and therefore, and more heat is given together with it from the friction zone.

The choice of optimal viscosity of the oil is complicated by the fact that it is very dependent on temperature. For example, when the temperature drops from 100 to 50 ° C, the viscosity may increase by 4-5 times. When cooling the engine oils up to 0 s and, especially before negative temperatures, their viscosity increases hundreds and thousands of times.

For many years, the study of the dependence of viscosity on temperature was proposed many ways to build viscosity characteristics and formulas expressing this dependence. But only a few of them give a satisfactory convergence of the results of the calculation and practical viscosity determination by the viscometer. This is primarily due to the fact that oils are liquids, whose molecules, having a complex structure, form various structures depending on both the molecular weight and the group chemical composition of the oil.

To describe the dependence of the viscosity of motor oils on temperature, the equations of Walter and the Soviet chemical cryptologist Ramayai are practically used.

Walter formula in exponential form has the form

where - kinematic viscosity, mm 2 / s, at temperatures t. , ° C; T.- absolute temperature; but- coefficient depending on the individual properties of the liquid.

For modern oils, the best coincidences with experienced data are obtained at a \u003d.0,6.

Ramaya formula has a view

,

where - dynamic viscosity of the oil; T.- absolute temperature;

BUTand IN- coefficients permanent for this oil.

The formula allows you to present the viscosity-temperature characteristic of the oil in the coordinates argument 1 / T. - Function
.

The practical application of both formulas showed a satisfactory coincidence of the calculation results with experienced data. The formula Ramaya gives a slight accuracy. The principal disadvantage of these equations is their empirical nature that does not open the essence of physical phenomena occurring in oils when their temperature changes.

Based on the Walter and Ramaya equations, special coordinate grids were built and printed, which can quickly build viscosity-temperature curves of various engine oils.

Almost the dependence of kinematic viscosity on temperature can be depicted in three coordinate systems. In the temperature range of 50-100 ° C is the easiest, the viscosity characteristic is to build in the coordinates T and (Fig. 1). With a wider range of temperatures, for example, on the oil temperature of up to 100 ° C, it is recommended to use Ramaya coordinate grid (Fig. 2).

The problem of quantitative assessment of the steepness of the viscous and temperature curve is very important. Several such estimated parameters are proposed.

1. Kinematic relationship sky viscosity v. sO. andv. 100 . This simple and reliable parameter characterizes the steepness of the viscosity-temperature curve in a relatively narrow range of temperatures of the heated oil, but does not allow it to estimate it in the most important area of \u200b\u200blow temperatures that have a decisive effect on the engine's starting characteristics. For motor oils used in summer or in hot climate conditions, V 50 / V 100< 6; для масел, предназначенных к применению зимой и особенно в северных районах, v 50 /v 100 < 4.

2. Temperature viscosity coefficient (TCV) at temperatures from 0 to 100 ° C

TKV 0 -100 \u003d (V 0 - V 100) / V 50.

When evaluating the steepness of the viscous-temperature curve under conditions of low temperatures, the TKV gives a clearer picture than the ratio V 50 / V 100. For winter oils TKV 0-100<: 22, для всесезонных < 25, для летних < 35-40.

3. Viscosity index (IV). In modern domestic and foreign standards, an IV indicator based on comparing oil with two vehicles is used to estimate the steepness of the viscous-temperature curve.

One of these standards is characterized by a steep viscous-temperature curve, and the other is a canopy. Standard:

- with a steep curvethe viscosity index is assigned 0,

- And the standard with a canopy curve - 100.

The higher the IV oil, the more common viscosity and temperature curve and the better the oil for winter operation.

In fig. 3 shows a graph explaining the principle of determining the viscosity-temperature properties of oils with the help of IV. The graph shows the viscosity-temperature characteristics of three oils: two references (upper and lower curves) and one studied (average curve).

Virtually IV is calculated by the formula (GOST 25371-82)

Yves \u003d (V - V 1) / (V - V 2), or Yves \u003d (V - V 1) / V 3,

where V is the kinematic viscosity of the oil at 40 ° C with Yves \u003d 0 and having at 100 ° C as a kinematic viscosity as the test oil, mm 2 / s; V 1 - kinematic viscosity of the test oil at 40 ° C, mm 2 / s; V 2 - the kinematic viscosity of the oil at 40 ° C with Yves \u003d 100 and having at 100 ° C as a kinematic viscosity as the test oil, mm 2 / s; V 3 \u003d V-V 2.

Viscosity It is called the property of fluid to resist when it moves its layers under the action of external force. This property is a consequence of friction arising between liquid molecules. There are dynamic and kinematic viscosity.

Viscosity varies significantly with temperature change. With a decrease in temperature, the interaction between molecules is amplified, and the viscosity of the oil increases. For example, when changing the temperature by 100 ° C, the viscosity of the oil may vary 250 times. Considering the linear character of the dependence, it is possible to determine the viscosity of the oil at any temperature by the nomogram.

With an increase in pressure, the viscosity of the oil increases. Pressure values \u200b\u200bin the oil film concluded between rubbing surfaces can be significantly higher than the loads themselves on these surfaces. In the oil film of the indigenous bearing of the crankshaft engine, the pressure value reaches 500 MPa.

With an increase in pressure, the viscosity of more liquid oils (with a canopy viscosity-temperature characteristic) increases to a lesser extent than more viscous oils (with a coolest viscous temperature characteristic).

At pressure (1.5-2.0) 10 3 MPa, mineral oil solidifies. The injected additives in the base oil contribute to maintaining the carrier ability of the oil layer while increasing the load.

Viscosity It is the main parameter during the selection of oil, so it is always indicated in the marking of the oil. For marking, viscosity is determined at those temperatures under which friction nodes work. Motor oils for internal combustion engines are marked by kinematic viscosity mm 2 / s (CST) at a temperature of 100 ° C, which is accepted as the average oil temperature in the engine (crankcase, lubrication system).

To obtain oils with good viscous temperature properties, low-viscous oils are used as basic, having a viscosity of less than 5 mm 2 / s at a temperature of +100 ° C, and viscosity additives (thickeners) are added to them. Polymer compounds such as polyisobutylene, polymethacrylates, polyalkylstyrenes, etc. are used as additives.

FROM decrease in temperature The volume of the polymer macromolecule decreases (the molecules "coagulate" into the tangles). For increase temperature Tangles macromolecules "unfold" into long branched chains, connecting the base oil molecules, the volume of them becomes greater, and the viscosity of the oil increases.

Thicken oil additives They have a necessary level of viscosity at positive temperatures of 50-100 ° C, a common viscosity change curve (Fig. 4) and, consequently, a high viscosity index of 115-140. Such oils were called all-season, as they simultaneously have the properties of one of the winter classes and one of the summer.

Fig. 4. Effect of viscosity additives on oil viscosity

at different temperatures:

1 - low-viscous oil; 2 - the same oil with viscous

additive (thickened)

In the lubrication systems of modern automotive engines, precisely thickened all-season oils are used. When using their use, the engine power rises by 3-7% (which is provided by the high viscosity index and the ability of thickened oils to reduce viscosity in friction pairs at high shift rates), it is easier for the start and reduces the warm-up time, the mechanical losses for friction are reduced, and, as a result, Fuel consumption, the durability of parts and oil life increases. Fuel economy reaches 5% for large runs and 15% with short runs in winter with frequent engine launches (Fig. 5).

Fig. 5. Reducing gasoline consumption when moving a car

as the engine warms up

To disadvantages of thickened oilsbelieve the low stability of thickened additives at high temperatures, which causes the deterioration of the viscosity-temperature characteristics of the oils with a long permanent operation of them in engines.

Viscosity index (IV), Assessing the viscosity-temperature properties of oils, is a conditional indicator characterized by the degree of changes in the viscosity of the oil depending on the temperature and determined by comparing the viscosity of this oil with two reference oils, the viscosity-temperature properties of one of which are taken for 100, and the second - for 0 units.

The viscosity index is determined by the nomogram (Fig. 6), calculated by or by special tables. To determine the IV by nomogram, it is necessary to know the values \u200b\u200bof the kinematic viscosity of the oil at temperatures of +50 ° C and +100 0 C.

Fig. 6. Normogram for determining the viscosity index of motor oils

The higher the IV, the more common curve (Fig. 7), the oil is characterized by oil and the better its viscosity-temperature properties. Of the two oils with the same viscosity at a temperature of +100 ° C, but with different Yves, one (1) can only be used in a warm time, since at low temperatures it loses mobility, and the other (2) is all-season, as it will provide Easy engine start at low air temperatures and liquid friction at operating temperatures.

Fig. 7. Dependence of the viscosity of motor oils from temperature

for different viscosity index values: 1 - IV 90; 2 - IV 140

Considering the fact that the viscosity of the oil and the viscosity index determine the performance of the friction assembly, then in the standards for oil, these parameters are normalized in quantitative terms. For automotive oils IV should not beshe is 90.

Therefore, in the production of motor oils, it is necessarybye available and efficient methods reduce dependencethe viscosity of the oil on temperature, i.e. increase their Yves and downgradefrozen temperature. This applies primarily to winterand all-season brands of oils.

Temperature characteristics of motor oils are as follows:

Flash temperature - The lowest temperature in which the pairs of heated in standard oils form a mixture with air, which flashes from open fire, but quickly goes out due to insufficient intensive evaporation.

Flammation temperature - The temperature in which the pairs of heated oil are formed with air such a mixture, which is flammable and lit from open fire at least 5 s. Flash temperature is an indicator of fire-hazardous oil. It can be judged by the presence of volatile fractions in oil, which can quickly evaporate in the running engine and increase the oil consumption on the avgar. The decrease in the oil outbreak temperature indicates fuel oil dilution.

Frozen temperature (The temperature of the yield) is the lowest temperature at which oil still has some fluidity. The temperature determined under standard conditions is 3 ° C above the active solidification temperature at which it is in a fixed state for 5 with the oil.

Perpeneum temperature - The one at which the small paraffin crystals appear and the oil purges. Subsequently, the crystals form a frame and oil loses mobility. Between crystals, the oil remains still liquid and with strong shaking oil fluidity can be recovered. The closet temperature depends on the cooling rate, heat treatment and mechanical effects.

Frozen temperature serves as the maximum minimum temperature of the casting and, partly, oil operation. The minimum operating temperature of the engine oils is determined by low-temperature viscosity and pumping characteristics.

Throat - Property that determines the loss of oil fluidity. When the temperature decreases to a certain value, the oil fluidity is reduced, and with further decrease it is free. With an increase in the viscosity of the oil, the most high-elect hydrocarbons (paraffin, ceresine) are distinguished from it, and with complete loss of oil fluidity, microcrystals of solid hydrocarbons (paraffin) form a spatial crystal lattice that binds all the oil into a single immobile mass.

The temperature at which oil loses fluidity is called the temperature of the frost. Lower temperature limit of oil use of approximately 8-12 ° C above the frosted temperature, i.e.:

t ov \u003d t 3 - (8-12) ° C,

where: T ov is the lower temperature limit of the ambient air (the use of this brand of engine oil), 0 C;

t 3 - The temperature of the frozen of a certain brand of oil, regulated by the standard, 0 C.

Reducing the temperature of the oils is achieved by dewaxing (partial removal of paraffins) or adding depressor additives during their production. Depressors prevent the formation of a crystal lattice when paraffin crystals are combined into bulk structures. Lowering the oil temperature, depressors do not affect its viscosity properties.

Anti-wear (lubricatingproperties Characterize the ability of oil to prevent the wear of the friction surfaces. The robust film formed on the rubbing surfaces eliminates the direct contact of the parts. High anti-wear properties of oil are especially in demand with small frequencies of rotation of the crankshaft, when high specific loads, as well as the geometric shapes or dimensions of parts have significant deviations, which is fraught with scams, setting and the destruction of rubbing surfaces.

The anti-wear properties of oil depend on its viscosity, the viscosity-temperature characteristic, lubricating, oil purity.

With an increase in oil temperature, the adsorption layer is weakened, and when the critical temperature is reached, 150-200 ° C, on the edge of the strength of the film and dry friction, is destroyed. Oils with high anti-wear properties are able to form a friction mode to prevent wear, which eliminates the immediate contact of the driving surfaces of metals. Therefore, it is possible in this case the wear is caused by the cyclical of the loads in the individual sections of the friction surfaces and fatigue destruction of the metal (fatigue cracks in the pile of crankshafts).

About lubricating ability ("oiliness") oil They are judged by its chemical composition, viscosity, presence of additives. The oils contained in oils and having high surface-active properties of resinous substances, high molecular acids, sulfur compounds are affected and having high surfactants.

The correct choice of viscosity of the oil is largely affected by the wear rate. High-viscosity oils at low temperatures thickens and do not go to the rubbing surfaces of parts. At the same time, the start and engine warming on less viscous (liquid) oils is facilitated, the liquid friction mode comes faster.

Antifriction additives are introduced to reduce friction losses in engine oils, the basis of which serve precipitated organic compounds containing noble elements (nickel, cobalt, chromium, molybdenum). Low-soluble surfactants of this type form multilayer protective films in the embodiments of friction with the introduction of alloying metals into the friction zone. This particular place belongs to molybdenum, the atoms of which are able to associate iron atoms and form structures resistant to pitting (local painting of metal), fretting corrosion, etc. Moreover, only this metal forms as a result of oxidation of surface layers of oxides, melting point and hardness which are an order of magnitude lower than that of the metal of the friction surface.

Motor oil lubricating properties, like oils for other machines and mechanisms, due to its viscosity and oiliness, the influence and mechanism of action of which are different.

Viscosity as a property associated with internal (molecular) friction exhibits itself with liquid (hydrodynamic) friction. Oil oil is important when boundary friction occurs. Under these conditions, the strength of the oil film is a decisive factor that impede the direct contact of the driving parts.

It has been established that the strength of the oil film depends on the polar activity of oil molecules, i.e., from their ability to form strong layers of strictly oriented molecules.

An indicative field of polar-active molecules forms a kind of pile on the surface of the rubbing parts. The longer the polar-active oil molecules and the stronger they are connected to the surface of the rubbing parts, the higher the oil oil. But this is a very simplified explanation, which allows you to understand only the basic essence of this phenomenon.

In fact, in real conditions, it is usually not monomolecular, and multimolecular oriented layers, in which intramolecular friction acquires a particular nature, which consists in the fact that friction occurs between the individual layers of molecules, and not between individual molecules. With the corresponding selection of polar-active substances included in the oil, the number of layers can reach thousands and more, and their total thickness up to 1.5-2 microns. With increasing temperature, the upper layers that do not have a solid connection with the surface of the part, destabilize and destroy, but the first monomolecular layer is difficult to destroy.

It was experimentally established that the friction coefficient between the parts depends little on the number of monomolecular layers and almost the same at one and several dozens of such layers. This can be explained by the fact that it is enough to add very few substances that have high polar activity as oil oilyness, i.e. the strength of its oil film increases sharply.

The processes associated with oiliness are studied on special friction machines. The quantitative definition of lubricating properties of oils is carried out using a four-haired machine (GOST 9490-75 *). The principle of action of this car is as follows.

Three balls with a diameter of 12.7 mm made from steel SH-15 (Bearing series) installed motionless in the form of a triangle in a special cup-shaped clip, into which the test oil is then poured. These balls are superimposed on top of the same ball (fourth), fixed in rotating, like a drilling machine, spindle.

Spindle speed 1460 ± 70 min -1. Turning the lower balls during the test is not allowed.

On a four-haired machine, a series of definitions are carried out, each of which is performed on the new sample of the test oil and new balls. On the car determine critical load, welding load, index of the loop and displaytel wear. When determining the first three parameters, the test duration is 10 0.2 s, when evaluating wear indicators - 60 0.5 min. The regime load must be respected in accordance with the standard.

The zadira index and the critical load characterize the ability of oil to protect rubbing surfaces from damage and scaling, and the welding load evaluates the limit load that this oil can withstand. The wear indicator determines the effect of lubricating material on the wear of the lubricated surfaces.

It is estimated by the diameter of spots (traces) on all three lower balls. Measurements are carried out by a microscope with a 24-fold increase and the counting scale with a division price of not more than 0.01 mm. Each stain is measured in two directions: in the direction of sliding and perpendicular to it.

The result is the average arithmetic average of all measurements in three lower balls.

The principle of operation of the four-haired machine is shown in Fig. eight.

Fig. 8. Principle of action of a four-fold machine

to determine the anti-wear and anti-promotional properties of oils:

but- loading diagram of ball pyramid; B - Scheme

four-haired clip; in- the design of the main node;

1 - fixed balls; 2 - rotating ball;

3 - The studied oil

Antioxidant properties Characterized by the resistance of oil to oxidation and polymerization during the engine operation, as well as decomposition during storage and transportation.

The duration of oil in the engine depends on its chemical stability Under which the ability of oil is understood to maintain its initial properties and resist the external influence at normal temperatures.

The stability of motor oils affect the following factors: chemical composition, temperature conditions, oxidation duration, catalytic action of metals and oxidation products, oxidation surface area, water presence and mechanical impurities. Increased air pressure accelerates the process of oil oxidation, as the process of its mutual diffusion with air is enhanced.

On the oxidation process, the decisive effect has temperature. Oils stored at a temperature of 18-20 ° C retain their initial properties for 5 years. Starting from 50-60 ° C, the oxidation rate doubles with increasing temperature for every 10 ° C. Therefore, the high thermal tension of the parts of the forced engines, with which you have to contact the engine oil, and interacting with the combustion chambers breaking into Carter (on the compression tact of their temperature is about 150-450 ° C for gasoline engines and about 500-700 ° C for diesel engines ) The conditions for their work sharply deteriorate. The increase in the thermal tension of motor oils is also associated with separate design solutions: Uploading; use of a sealed cooling system (increases the temperature of the piston by 10-20 ° C); Reducing the volume of the engine lubrication system; Oil cooling pistons and others.

Thermo-oxidative stbureliness Defined as oil resistance to oxidation in a thin layer at elevated temperature by estimating the strength of the oil film.

To slow down the reactions of oxidation and reduce the formation of deposits in the engine in the oil, antioxidant additives are introduced into the oil.

Detergent - dispersing (detergent) The property of oil is called its ability to prevent the sticking of carbon particles and hold them in a stable suspension state, which significantly reduces the processes of formation of lacquer sediments and on the hot surfaces of the engine parts.

When using oils with good dispersing properties, the parts of the engines look clean, as if flushed, hence the appearance of the term "detergents".

Dispersing properties of oils are estimated in points from 0 to 6 by the PVV method. The formation of lacquer sediments on the parts of the engine operating on oils with detergent additives is reduced by 3-6 times, i.e. from 3-4.5 to 0.5-1.5 points.

Washing additives There are ash and relaxed. The ash additives contain barium and calcium salts of sulfic acid (sulfonates), as well as alkyl phenolates of alkaline earth metals barium and calcium. Oils with ash additives in an amount of 2-10%, burning, form ash adherent to the surface of the parts. Papered detergent additives do not form ash when combustion of oils, since they do not contain metals.

Corrosion properties Oils depend on the presence of organic acids, peroxides and other oxidation products, sulfur compounds, inorganic acids, alkalis and water.

Corrosion of fresh oil, in which natural organic acids and sulfur compounds are present, is insignificant, but sharply increases during operation. The presence in fresh oils of organic (naphthenic) acids is associated with their incomplete removal during the cleaning process.

The corrosion effect of oils is also associated with the content of 15-20% of sulfur compounds in them in the form of sulphides and. The components of residual sulfur, which at high temperatures lead to the release of hydrogen sulfide, mercaptans and other active products. In high temperatures, sulfur compounds are especially aggressive with respect to silver, copper, lead. In the process of using oil, the acid content in it increases by 3-5 times, which depends on its chemical stability, the content of antioxidants and working conditions.

Evaluation of corrosion resistance They are produced at an acidic number, which for fresh oils does not exceed 0.4 mg of KOs per 1 g of oil. In corrosivity, this concentration is practically not dangerous.

Corrosion processes in the engines slow down the neutralization of acidic products by introducing anticorrosive additives; slowing down the oxidation processes by adding antioxidant additives to oil; creation on the surface of the metal (in the manufacture of parts) by a resistant protective passivated film from organic compounds containing sulfur and phosphorus.

Known additives and corrosion inhibitors and their compositions that reduce all types of wear.

Selection of oil With optimal values \u200b\u200bof operational properties, it depends on the design and mode of operation of the friction assembly.

Viscosity - One of the most important properties of oil that has a multilateral performance. The viscosity variability of friction pairs, heat removal from working surfaces and sealing gaps, energy losses in the engine, its operational properties detects. The speed of the engine start, pumping the oil on the lubrication system, cooling the rubber surfaces of the parts and their purification from contaminants is also dependent on the viscosity-temperature properties of the oil.

Increased viscosity oils are used for high-loaded, low-speed or working in the conditions of intense thermal mode of engines. At the same time, the higher the viscosity of the oil in the engine running, the more reliably the seal, the probability of gases breakthrough, below the oil of the oil. Therefore, large viscosity oils are used in cases where the engine is worn, the gaps are increased or operating conditions are characterized by high dusting, increased temperature varying in large loads.

Oils with less viscosity are used for low-loaded high-speed engines. They facilitate the start of the engine, it is better pumped through the lubricant system and cleaned from mechanical impurities, provide a good heat removal from the working surfaces of parts.

Oil temperature Significantly affects its kinematic viscosity. With a decrease in temperature, viscosity increases, and with an increase - decreases. The smaller the viscosity difference depending on the temperature, the greater the oil satisfies the operational requirements.

An increase in viscosity of oils with a decrease in temperature leads to significant difficulties when using cars, especially in the winter season when engines start. At negative temperatures in the range from -10 ° C to -30 ° C, the moment of resistance to turning the crankshaft of the engine is sharply increases, the minimum starting frequency of rotation is slower, the oil supply is worsened to the rubbing surfaces of the parts.

Reliable start of gasoline engines It is carried out at the values \u200b\u200bof the rotational speed of the crankshaft in the range of 35-50 min -1 at the ambient temperature of -10 0 C ... -20 0 C, and diesel engines with different ways of mixing - on average in the range of 100 - 200 min -1 at temperatures 0 0 C. The viscosity of the engine oil, at which the launcher of modern engines of various designs does not rotate the crankshaft, changes in the range (4 - 10) · 10 3 mm 2 / s. Therefore, to ensure the start of the engine in the cold time, motor oils must have a low viscosity at negative temperatures.

Any modern car does not cost without butter, which is also in the engine, also poured into a transmission. There is a whole variety of this consumable material on the market and there is a whole table of viscosity of motor oils. The designation of viscosity in it makes it possible to easily choose the composition necessary for its vehicle. It is only necessary to understand this indicator well as viscosity.

What it is? Why is viscosity so important? And in general, what important role plays the oil in the engine or in the transmission elements? Replies to these and other questions will be presented in this article.

Key role of oil

The importance of the presence of oil in the engine is difficult to overestimate, since it is entrusted with the most responsible task - to reduce the friction of the surfaces of the parts. Unfortunately, not all drivers give this value. There are those who forget about oil in general and then, ultimately, the engine is completely out of order due to significant damage.

However, engine oil has one more equally important property depending on the viscosity index. The fact is that due to oil lubricant, the efficiency of the antifreeze is noticeably improved, and this prevents engine overheating.

During the engine operation, mechanical and thermal processes are constantly occurring in it, due to which it may be overheated. Due to the circulation of engine oil, which gets to many parts, the extension of excess heat occurs effectively from the power plant. At the same time, it is distributed between all the surfaces to which it comes.

But, in addition to the heat removal and reducing friction, the engine oil collects different "garbage". As a result of the friction of parts, metal dust is formed, which looks like chips on some car models. Circulating the engine, oil due to its viscosity, collects this dust, which then settles in the filter.

According to the viscosity table, the efficiency of work depends on kinematic viscosity. Therefore, it is worth reading this characteristic.

What to understand the term viscosity?

We all have heard that the oil has viscosity, but what it specifically understands not everyone. Under this definition, the basic quality indicator of the consumable material can be considered. In other words, viscosity is the ability to maintain its flowable properties under the influence of temperature drops. That is, from the lowest indicators in winter to the highest values \u200b\u200bin the summer, with maximum loads on the engine.

At the same time, the value is not permanent, and temporary and depends on a number of factors, including:

• engine design;
• mode of operation;
• degree of wear of parts;
• environmental temperature.

In all countries of the world, a single oil was introduced without exception - SAE J300, which can be represented as a table of viscosity of motor oils. The first three letters are the designation of the American Society of Automotive Engineers. In English it looks like this: Society of Automotive Engineers.

According to this system, the conditional units that are labeled by the brand is indicated by the degree of viscosity on the SAE VG (Viscosity Grade). It is worth considering how it is subdivided by consumables.

Kinematic and dynamic viscosity

There are two concepts of viscosity of motor oils:

1. kinematic;
2. dynamic.

Kinematic The viscosity is called oil ability to maintain its fluidity in a normal or high temperature. In this case, the norm is considered to be 40 ° C, and increased - 100 ° C. For measuring the kinematic viscosity of engine oil, special units are used - Santistoks.

W. dynamic Or absolute viscosity there is no dependence on the density of the consumable material. Here the resistance force of two layers of oil, located at a distance of centimeters and moving at a speed of 1 cm / s. Measurement is carried out using special equipment - rotational viscometer. The device is able to recreate the operation of motor oil in conditions as close as possible to real.

Features of the classification of motor oils

Depending on the extent of the flow rate of the total there are 12 classes of lubricants. In this case, all fluids belong to winter and summer varieties (according to 6 classes, respectively). Each marking has a digital or alphanumeric designation (or viscosity index).

By and large, any oil is capable of working under any conditions. However, for SAE indicators, the lower temperature limit is assigned an important role. In oils with the prefix W to the index (from the word Winter - Winter) there is a low temperature threshold. This means that the engine launch in winter (in particular frosty conditions) will be made safely.

Separate classifications are honored by all-season motor oils. By SAE, they have a double designation. That is, first indicates the value of kinematic viscosity in the course of successful tests at the lowest, as far as possible, temperature. The second value, as can be understood, with the most maximum.

Some manufacturers in the designation of certain oils use the letter W. So immediately you can guess that it is winter engine oil. All six classes are marked as follows:

If necessary, to find out at what negative temperature the car successfully will be completed, it follows from the designation facing the letter W, take away 40. For example, interests oil under the SAE 10W index. After easy calculation, we obtain the desired value of -30 ° C.

That is, a special viscosity table can not even use. Although it will not hinder reliability to make sure the correct choice.

Summer oils

In the classification of oils in SAE, there are no letters in the designation in the designation, it is also clear. And their classes in the table look like this:

The greater the index, the higher the viscosity of the oil. That is, for a hot climate it has a more dense consistency. For this reason, such oils are not allowed at least 0 ° C at ambient temperature. Due to its viscosity, they best show their properties only in summer heat.

All-season motor oils

Combine all the properties of winter and summer oils. Therefore, they also have a joint designation, separated by a dash. For instance:

1. 0W-50;
2. 5W-30;
3. 15W-40;
4. 20W-30.

Using other designation for all-season oils is not allowed (SAE 10W / 40 or SAE 10W / 40).

It is this type of consumed material that was most common among most drivers, due to a special class of viscosity of engine oil. No need to change the oil twice per season. However, the all-season oil is suitable only to those who live in the middle lane, where the climate is more favorable.

What is affected by the wrong choice of engine oil?

Typically, car manufacturers for each engine select individual oil yielding indicators. This allows you to increase the efficiency of the engine with its minimum wear. For this reason, it is necessary to adhere to the recommendations of the automaker in relation to each specific model. And the advice of acquaintances and friends, especially unauthorized persons who are workers a hundred, it is better not to perceive for the truth.

However, human curiosity will never be limit. What can happen if the engine oil is used? Here are two outgoings:

• Low-temperature viscosity. In severe frosts, such oil has a very dense consistency, which makes it difficult to supply the pump to the engine. Motor oils with low-temperature viscosity there are no such problems (for example - 5W). As a result, some time the motor after starting will work "in dry". And while the lubricant will still get to the rubbing details, they will have time to overheat and wear out.
• In the heat, the situation will not be in the best way. Motor oil becomes too liquid, and therefore it is not able to linger on the details and create the necessary lubricant layer. The first victim of such oil starvation is usually camshaft.

In this regard, it is necessary to choose the right oil for your car to avoid serious consequences. The main thing is that the viscosity corresponds to the conditions under which the car is operated.

Common mistakes

Unfortunately, not all drivers prefer to choose lubricant according to the classification of oils by SAE. There are two main mistakes among them. Lovers of fast ride refuse to lubricate and prefer sporting varieties. However, this is a sure way to bring the engine of your car to the "Mortal Odra". This is the first error.

Others adhere to the second erroneous opinion. According to the owners of old cars, at that time there was still no good engine oil, which would fully satisfy the needs of the "old women." Most of them are already tuned to overhaul.

This is fundamentally incorrect because at each stage of the improvement of the production technologies, at the same time the development of suitable engine oil was also conducted. Two concepts (engine and oil) as it were for one whole, and disconnect them unacceptable.

In addition, many compounds in addition to the oil component had various additives of synthetic origin. Therefore, the experience of the vehicle does not matter here.

Finally

The table is not easy because it is due to it that you can choose the necessary lubricant for a longer and efficient engine operation. It should be remembered that the engine needs not only in regular maintenance, but also in the timely replacement of all consumables, including lubricating agents.

What is hhs?

As you know at high temperatures, the viscosity of the engine oil decreases, the oil film becomes thinner. Parameter HHS. - This is a high temperature viscosity at high shear speed. HHS. Measured in millipascals per second. The most common method of test ASTM D 4683. This method includes determining the viscosity of the oil at high temperature 150c. so HHS. - This is the viscosity of the engine oil at a temperature of 150c and a high shift rate of 106 s -1. Nothing hard for understanding here is not - just need to remember that for each car your interval is permissible HHS.. In the engine not intended to use motor oils with low HTHSin no case cannot pour such oils. Why and you need to pay attention to the manufacturer's recommendations, choose oil in accordance with the recommended viscosity recommended by tolerances and recommended standards.

Applying oil with reduced HTHS In not intended for this, the engines can lead to their accelerated wear. In motors designed to use oils with reduced HHS.There are a number of significant differences:

• the distance between rubbing surfaces is reduced. Higher accuracy of assembly and fitting parts to each other (minimum gaps between the details).
• the use of widespread bearings in which high viscosity oil comes slower.
• special application of the surface microprophil on the details - on the chimney in the cylinders, to hold on the details of low viscosity oils.

If the engine is not designed for low-voltage oils with low HHS., the use of such oils in it is unacceptable!

What is used with low HTHS oils?

In the last decade among world automakers, there is a tendency to reduce high-temperature viscosity at high shift speed - HHS.The use of such oils is economically and environmentally limited. Oils with low HHS. Give greater fuel savings compared to conventional higher viscosity oils. A smaller viscosity of the oil leads to a smaller resistance to the engine parts, which leads to an increase in the engine power, less wear in some engine nodes. The use of such oils, also positively affects the ecology. CO2 release into the atmosphere on low viscosity oils is significantly lower than on higher viscosity butters.

What parameter hhs is safer for the engine?

Let's try to show clearly at what values \u200b\u200bof HHS is dangerous, and at what no danger is for the engine.

A document published in the Japanese scientific publication of the Institute Toyota R & D In 1997. (Here you need to make a discount for a year, many years have passed and low-viscous oils have become much more stable and safer than it was at the time of 1997.)

So a group of Japanese scientists:
Toshihide Ohmori.
Mamoru Tohyama. - Toyota Central R & D Labs., Inc.
Masago Yamamoto. - Toyota Central R & D Labs., Inc.
Kenyu Akiyama. - Toyota Motor Corp.
Kazuyuoshi Tasaka. - Toyota Motor Corp.
Tomio Yoshihara. - Lubrizol Japan Ltd.

Conducted an experiment on 1.6 DOHC four-cylinder engines. The main goal of experiments is to find out how oils with different HTHS affect engine wear. As affected by wear, adding friction modifiers to motor oils, based on ModTC (organic molybdenum). In the engines flooded oils of different viscosities with different HTHS (high-temperature viscosity at high shift speed) after some "run" the engines disassembled and investigated for wear of parts.

HHS oils of two main associations.

ACEA A1 Hhs ≥ 2.9 and ≤ 3.5 xw-20 ≥ 2.6
ACEA A5. HTHS ≥ 2.9 and ≤ 3.5
ACEA A3. HTHS ≥ 3.5

ILSAC GF-4 referring to J300.
5W20 HTHS is at least 2.6.
5w30 HTHS at least 2.9
0W-40, 5W-40, 10W-40 HHS ~ at least 3.5

Fig. 1. Wear piston rings at a temperature of 90c and at extreme temperatures 130c

At the viscosity of HHS 2.6, there is a "border wear zone" - threshold below which a significant increase in wear begins, if HHS is less than 2.6, the wear increases very much, if more than 2.6, then the wear line is almost at the same level. By 2.6 wear slightly higher than 3.5. The higher the engine revolutions - the wear of the piston rings increases.

Figure 2. Wear cams. At 90 degrees at HHS 2.6, even smaller camber wear is observed than at HHS 3.5. But with an increase in temperature to 130s - everything changes - again 2.6 border zone. HTHS is less than 2.6 - wear rises, more than 2.6 - the depreciation is minimal.

Figure 3. Wear connecting rod bearings. The wear is not particularly visible - lines direct, but still there is a small tendency to reduce wear towards HHS 3.5

Figure 4. Added various friction modifiers and compared with conventional oil without modifiers.

Fig. five a) First picture on ordinary oil, b) The second oil with a modster friction modifier is organic molybdenum. ModTC really reduces friction and prevents wear, and the lower the viscosity of the oil and HTHS, the greater the need for such an additive.

PS. The study was conducted more than 10 years ago, from that time, low viscosity oils changed for the better! Therefore, the "border zone of wear" - it may well be a normal point where it is still far from wear. Or maybe not - physics! We have to find out!

So is it worth pouring low grade oils?

1. Along with the pluses of low grade oils - fuel economy, ecology, higher efficiency, have cons! For example, many manufacturers in manuals, where low-grade oils are recommended, "5W-20 is not recommended not recommended at high speeds". That is, manufacturers believe that at high speeds, at high ambient air temperatures, with heavy loading of the car, such oils are better not to apply. The fact is that too thin film at high speeds, with concomitant factors, it may not be enough to protect the friction pairs from wear. Recently, with the course of oil progress 5W-20, 0W-20 improved! New friction modifiers appeared (three-nuclear molybdenum, titanium oxidesTD), improved base oils and anti-wear additives. Such inscriptions in the manuals began to disappear - they stopped being relevant. Automakers are now on the contrary, they write in the manuals "The use of motor oil 0W-20 in your engine is preferable" counting that this oil specifically does not harm this engine. In any case, you need to listen to manual manufacturers, they have more experience and reason to believe so.
2. With an abnormal situation, you did not start the car in the frost, the fascinating fuel falls into the engine oil and dilutes it. Low viscosity oil, when fuel in it, becomes even less viscosity. Fuel, of course, evaporates with time warming up, but for some time there can be a very low viscosity oil.

Example 1: If someone thinks that "low-grade oils will necessarily lead the engine to elevated wear" - it is mistaken. I will give the test results on the tribological installation - the 4-ball turning machine of friction.

Tribological tests of oils on the diameter of wear under load 392n and 1 hour:
See who in the lead leaders? Oil 0W-20.

Example 2:Laboratory tests of workouts 0W-20, 5W-20 in severe Russian conditions:

Output: This article corresponded to me twice with a break in 4 years. At first, I scared the public with low grade oils, but time went, we gained experience, made laboratory tests and came to the conclusion - that nothing bad in oils 0W-20, 5W-20, 0W-16 - no. If they are recommended by the manufacturer of your car! Low viscosity oils are faster on working viscosity - they themselves are less viscosity. Such oils saved fuel when the car warms in the morning. Low viscosity oils save fuel at engine operating temperature - when the engine is completely warm. In some engines equipped with hydrocompensators, they work quieter in hydrocompensators. With low-temperature start, low viscosity oils faster go into all hard-to-reach engine locations. In many engines, it is structurally provided for nozzles of cooling pistons that water the piston of oil - in this case, it is better and faster than low viscosity oils. That is, with small disadvantages or their complete absence, we get a lot of advantages from using low grade oils.

Fig. 5 a) First Picture on Conventional Oil, B) The second oil with a modster friction modifier is organic molybdenum. MODTC really reduces friction and prevents wear, and the lower the viscosity of the oil and HTHS, the greater the need for such an additive. The study was conducted more than 10 years ago, from the time of oil the low grade changed for the better! Therefore, the "border zone of wear" - it may well be normal oil. Or maybe not - physics ... We still have to know!

What parameter hhs choose?

The main negative factors when using low-grade oils are:

High speeds, car loading, high ambient temperatures. But along with the advantages of low grade oils - fuel economy, ecology, higher efficiency, have cons! For example, many manufacturers in manuals, where low-grade oils are recommended, "5W-20 is not recommended not recommended at high speeds". That is, manufacturers believe that at high speeds, at high ambient air temperatures, with heavy loading of the car, such oils are better not to apply. The fact is that too thin film at high speeds, with concomitant factors, it may not be enough to protect the friction pairs from wear. Other automakers, on the contrary, write in manuals "The use of engine oil 0W-20 in your engine is preferable" counting that this oil specifically does not harm this engine. In both cases, you need to listen to manufacturers manuals, they have more experience and reason to believe that. Therefore, always when choosing a viscosity of the oil, follow your manual!

Abrasive deposits in the engine. Another problem when using low-grade oils - abrasive deposits in the engine. These are dust particles, ash, soot. These sediments in the engine adversely affect the too thin oil film, as if breaking it - which inevitably leads to elevated wear. In our difficult operating conditions - such deposits can be obtained very simple. We refrained by poor gasoline during the combustion, which was formed by an abrasive grainy ash, put a poor-quality air filter, an abnormal air seats in addition to the air filter. etc.

Motor oil dissolution fuel. In severe operating conditions, in Russia - frosts are not uncommon. With low-temperature starting engine, very often not ignited fuel falls into engine oil and dilutes it. Unless liquid low viscosity oil, when fuel appeared in it, becomes "like water". Fuel, of course, evaporates with time, but the oil does not restore its initial characteristics.

Output: In our conditions, with our gasoline, cork, heat, load, low-quality consumables, etc., "border zones" (threshold below which a significant increase in wear begins) with HTHS 2.6 nothing! With hhs ≥ 2.9 and above - wear engine wear less! If your manufacturer recommends, along with 0W-20, the viscosity of 5W-30 is that this viscosity will be preferable! If the manufacturer recommends only 0W-20, go to look for a manual from the same engine, in other US markets, Europe, Japan. If on the same engine, 5W-30 recommended in another country - then this viscosity is preferable!

There are car owners, with which the oils of 0W-20 and 5W-20 are preferable, for example, a car enthusiast of the car changes once every 3-5 years, there is no place to drive quickly, refills only on the verified refueling, where the default is good gasoline, on the XW-20 machine excellent It passes, and save a bunch of money for gasoline, for these 3-5 years.

The final choice for the motorist! Do you need a "border zone of wear" in favor of saving gasoline, or you need to have some, a small margin of calm, but a little more expense. Of course, it is necessary to look at the manufacturer's recommendation and choose from recommended viscosities! It is impossible to think that 5W-50 will save your engine from wear if only 0W20 and 5W30 is recommended in your engine worldwide. Moreover, at negative temperatures, 5W50 is usually much thicker than 5W-20, and wear on oil, such viscosity at low-temperature launches - much higher than on 5W-20 viscosity oils! Motor oils 5W-30 Regardless of whether ILSAC GF-4 is either ACEA A3 or ACEA A5 - are a kind of golden middle, where the oil film is not too thin, and in winter it is not so terrible!

Viscosity of motor oil - Basic characteristic on which lubricant is chosen. It can be kinematic, dynamic, conditional and specific. However, it is most often used to choose to choose a kinematic and dynamic viscosity. Their valid indicators clearly indicates the manufacturer of the car engine (often allowed two or three values). The correct selection of viscosity ensures the normal operation of the engine with minimal mechanical losses, reliable protection of parts, normal fuel consumption. In order to choose optimal lubricant, it is necessary to carefully understand the viscosity of the engine oil.

Motor Oil Viscosity Classification

Viscosity (another name - internal friction) in accordance with the official definition is the property of fluid bodies to resist the movement of one part of them relative to the other. At the same time, work is performed, which is dissipated in the form of heat into the environment.

Viscosity is a value of non-permanent, and it varies depending on the oil temperature available in its composition of impurities, the resource value (motor run on this volume). However, this characteristic determines the position of the lubricating fluid at a certain point in time. And when choosing one or another lubricating fluid for the engine, it is necessary to be guided by two key concepts - dynamic and kinetic viscosity. They are also called low-temperature and high-temperature viscosity, respectively.

Historically, it has so much that motorists around the world determine the viscosity of the so-called SAE J300 standard. SAE is an abbreviation for the name of the organization of the automotive engineers community, which is engaged in the standardization and unification of various systems and concepts used in the automotive industry. And the standard J300 characterizes the dynamic and kinematic components of viscosity.

In accordance with this standard, there are 17 classes of oils, 8 of them winter and 9 year old. Most of the oils used in the CIS countries have xxw-yy designation. Where XX is the designation of dynamic (low-temperature) viscosity, and yy is an indicator of kinematic (high-temperature) viscosity. Letter W means the English word Winter - Winter. Currently, most oils are all-season, which is reflected in such a designation. The eight winter is 0W, 2.5W, 5W, 7.5W, 10W, 15W, 20W, 25W, nine Summer - 2, 5, 7,10, 20, 30, 40, 50, 60).

In accordance with the SAE J300 standard, engine oil must comply with the following requirements:

• Pouring. This is especially true for the operation of low temperatures engine. The pump must freeze oil on the system without any problems, and the channels are not clogged with thickened lubricating fluid.
• Work at high temperatures. There is an inverse situation when the lubricating fluid should not evaporate, refine, and reliably protect the walls of parts by forming a reliable protective oil film on them.
• Engine protection from wear and overheating. This applies to work in all temperature ranges. Oil must provide protection against engine overheating and mechanical wear of parts surfaces during the entire operational period.
• Removing fuel combustion products from the cylinder block.
• Ensuring minimal friction force between individual pairs in the engine.
• Sealing gaps between the details of the cylinder-piston group.
• The heat dissipation from the driving surfaces of the engine parts.

On the listed properties of motor oil dynamic and kinematic viscosity affect each in its own way.

Dynamic viscosity

In accordance with the official definition, the dynamic viscosity (it is absolute) characterizes the power of the resistance of the oily liquid, which occurs during the movement of two layers of oil, removed to a distance of one centimeter, and moving at a speed of 1 cm / s. The unit of its measurement is PA C (MPa C). He has the designation in the English abbreviation CCS. Testing of individual samples is performed on special equipment - viscometer.

In accordance with the SAE J300 standard, the dynamic viscosity of all-season (and winter) engine oils is determined by this (essentially, the temperature of the rotationality):

• 0W - used at temperatures to -35 ° C;
• 5w - used at temperatures up to -30 ° C;
• 10w - used at temperatures to -25 ° C;
• 15w - used at temperatures up to -20 ° C;
• 20w - Used at temperatures up -15 ° C.

Also worth distinguish the temperature of the frozen and the temperature of the rocker. In the designation of viscosity it is precisely about pumping, that is, condition. When oil can freely spread through the oil system in permissible temperature framework. And the temperature of its complete pouring is usually a few degrees below (by 5 ... 10 degrees).

As you can see, for most regions of the Russian Federation oils with a value of 10W and above cannot be recommended for use as all-season. This is directly reflected in the tolerances of various automakers for machines implemented on the Russian market. Optimal for CIS countries will be oils with low-temperature characteristic 0W or 5W.

Kinematic viscosity

Another name is high-temperature, it is much more interesting to deal with it. Here, unfortunately, there is no such clear binding as the dynamic, and the values \u200b\u200bare of another character. In fact, this value shows the time for which a certain amount of fluid is poured through a hole of a certain diameter. A high-temperature viscosity in mm² / s is measured (another alternative unit of measurement of Sortistox - CST, there is the following dependence - 1 Ust \u003d 1 mm² / c \u003d 0.000001 m² / c).

The most popular high-temperature viscosity coefficients according to SAE - 20, 30, 40, 50 and 60 (Lower values \u200b\u200blisted above are rarely used, for example, they can be found in some Japanese cars used in the domestic market of this country). If you say in a nutshell, then the smaller this coefficient, the oil is fat, and vice versa, the higher it is thick. Laboratory tests are carried out at three temperatures - + 40 ° C, + 100 ° C and + 150 ° C. The device with which the experiments are carried out - rotary viscometer.

Three these temperatures are not chosen by chance. They allow you to see the dynamics of viscosity change under different conditions - normal (+ 40 ° C and + 100 ° C) and critical (+ 150 ° C). Tests are carried out at other temperatures (and according to their results, the corresponding graphs are built), but these temperature values \u200b\u200bare taken for the main points.

And dynamic and kinematic viscosity is directly dependent on the density. The relationship between them is as follows: Dynamic viscosity is a product of kinematic viscosity on oil density at a temperature of +150 degrees Celsius. This fully complies with the laws of thermodynamics, because it is known that with increasing temperature, the density of the substance decreases. And this means that with constant dynamic viscosity, the kinematic will decrease (as its low coefficients) will decrease. Conversely, with a decrease in temperature, kinematic coefficients increase.

Before switching to the description of the correspondences of the described coefficients, we will focus on such a thing as High Temperature / High Shear Viscosity (abbreviated - HT / HS). This is the ratio of the temperature of the engine to high temperature viscosity. It characterizes oil fluidity at a temperature test, equal to + 150 ° C. This value was introduced by the API organization in the late 1980s for the best characteristics of the produced oils.

Table of high temperature viscosity

Please note that in the new versions of the J300 standard, the SAE 20 viscosity oil has a lower boundary equal to 6.9 CST. The same lubricants in which this value is lower (SAE 8, 12, 16) are highlighted in a separate group called energy saving oils. According to the classification of the ACE standard, they have the designation A1 / B1 (outdated after 2016) and A5 / B5.

Viscosity index

There is another interesting indicator - viscosity index. It characterizes a decrease in kinematic viscosity with an increase in oil operating temperature. This is a relative value in which it is possible to conditionally judge the suitability of the lubricating fluid to operate at different temperatures. It is calculated empirically, comparing properties at different temperature modes. In good oil, this index must be high, because then its operational characteristics depend on external factors. Conversely, if the viscosity index of a certain oil is small, then this composition is very dependent on temperature and other operating conditions.

In other words, we can say that with a low coefficient, the oil is quickly diluted. And because of this, the thickness of the protective film becomes very small, which leads to significant wear of the surfaces of the engine parts. But the oil with a high index can work in a wide temperature range and fully cope with their tasks.

Viscosity index directly depends on the chemical composition of the oil. In particular, on the amount of hydrocarbons and the ease of the used fractions in it. Accordingly, the mineral compositions will have the worst viscosity index, usually it is in the range of 120 ... 140, in semi-synthetic lubricants, the same value will be 130 ... 150, and the "synthetics" boasts the best indicators - 140 ... 170 (sometimes even up to 180).

The high viscosity index of synthetic oils (in contrast to the mineral at their same viscosity according to SAE) allows you to use such compounds in a wide temperature range.

Is it possible to mix different viscosity oils

The situation is quite common when the car owner for any reason should be addicted to the engine of the engine with a different oil than that that is already there, especially, if they have different viscosity. Is it possible to do that? Reply immediately - yes, it is possible, however with certain reservations.

The main thing about to say right away - all modern engine oils can be mixed with each other. (different viscosity, synthetics, semi-synthetic and mineral water). This will not cause any negative chemical reactions in the engine crankcase, will not lead to the formation of sediment, foaming or other negative consequences.

Drop density and viscosity while increasing temperature

Prove it is very easy. As you know, all oils have a certain standardization of the API (American Standard) and ACEA (European Standard). In some other documents, security requirements are clearly spelled out, according to which any mixing of oils is allowed so that it does not cause any devastating consequences for the engine engine. And since the lubricating fluids correspond to these standards (in this case, it does not matter exactly the class), then the requirement is observed.

Another question is whether to mix oils, all the more different viscosity? It is allowed to make such a procedure only as a last resort, for example, if at the moment (in the garage or on the track) you do not have a suitable (identical to what is currently in the crankcase) oil. In this emergency, you can add lubricating fluid to the desired level. However, further operation depends on the difference of old and new oils.

So, if viscosities are very close, for example, 5W-30 and 5W-40 (and even moreover, the manufacturer and their class are the same), then with such a mixture you can easily ride and then before the next change of oil for the regulation. Similarly, it is allowed to mix and adjacent dynamic viscosity (for example, 5W-40 and 10W-40. As a result, you will get a certain meaning that depends on the proportions of the other composition (in the latter case, a certain composition with a conditional dynamic viscosity of 7.5W -40, subject to mixing their identical volumes).

Also allowed to long-term operation mixture of oil viscosity, which, however relate to neighboring classes. In particular, it is allowed to mix semi-synthetic and synthetics, or mineral water and semi-synthetic. On such compositions you can drive for a long time (albeit undesirable). But mix mineral oil and synthetic, although it is possible, but it is better to take it to it only to the nearest car service, and there is already a complete replacement of oil.

As for manufacturers, there is a similar situation. When you have different viscosity oils, but from one manufacturer - mix boldly. If you are good and proven oil (in which you are confident that this is not a fake) from the well-known global manufacturer (for example, such as or) add similar both by viscosity and in quality (including API and ACEA standards), then In this case, by car, you can also ride a long time.

Also pay attention to automakers tolerances. For some machine models, their manufacturer directly indicates that the oil used must necessarily comply with the tolerance. In the event that the lubricating fluid added does not have such a tolerance, it is impossible to ride for a long time on such a mixture. You need to replace as quickly as possible, and pour lubrication with the necessary tolerance.

Sometimes there are situations when the lubricating fluid needs to be pouring on the road, and you drive up to the nearest auto shop. But in its assortment there is no such lubricating fluid, as in the car carter. What to do in this case? The answer is simple - pour similar or better. For example, you use semi-synthetic 5W-40. In this case, it is desirable to pick up 5W-30. However, it is necessary to be guided by the same considerations that were given above. That is, oils should not be very different from each other according to the characteristics. Otherwise, the resulting mixture should be replaced as quickly as possible to a new grease suitable for this engine.

Viscosity and base oil

Many motorists are interested in the question of which viscosity has, and completely oil. It occurs because there is a common misconception that the synthetic means is supposedly viscosity better and that is why the "synthetic" is better suited for the engine of the car. And on the contrary, supposedly mineral oils have a bad viscosity.

In fact this is not true. The fact is that usually mineral oil itself is much thicker, so there is often such a lubricating liquid on store shelves with viscosity testimony by such as 10W-40, 15W-40 and so on. That is, low-viscous mineral oils practically does not happen. Another thing is synthetic and semi-synthetic. The use of modern chemical additives in their compositions allows to reduce viscosity, which is why oils, for example, with a popular viscosity of 5W-30 can be both synthetic and semi-synthetic. Accordingly, when choosing an oil, you need to pay attention not only to the value of viscosity, but also on the type of oil.

Basic oil

The quality of the final product largely depends on the base. Motor oils are no exception. In the manufacture of oils for the engine of the car use 5 groups of base oils. Each of them is distinguished by a method of producing, quality and characteristics.

At various manufacturers in the assortment, you can find a variety of lubricating fluids related to different classes, however have the same viscosity. Therefore, when buying a lubricating fluid, the choice of its type is a separate question that needs to be considered, based on the engine, brand and class of the machine, the cost of the oil directly and so on. As for the above values \u200b\u200bof dynamic and kinematic viscosity, they have the same designation according to the SAE standard. But here the stability and durability of the protective film in different types of oils will be different.

Select Oil

The selection of lubricating fluid for a particular engine engine is a time-consuming process, since it is necessary to analyze a lot of information to make the right solution. In particular, besides directly viscosity, it is advisable to ask the engine oil, its classes according to API and ACEA standards, type (synthetics, semi-synthetic, mineral water), engine design, and a lot more.

Which oil is better to pour into the engine

The choice of engine oil DOL is based on viscosity, the API specifications, ASA, tolerances and those important parameters that you never pay attention to. You need to select 4 main parameters.

As for the first step - the choice of viscosity of the new engine oil, it is worth noting that it is initially necessary to proceed from the requirements of the engine manufacturer. Not oil, but engine! As a rule, in the manual (technical documentation) there is a specific information about the lubricating fluids of which viscosity is allowed to be used in the power unit. Often it is allowed to use two or three viscosity values \u200b\u200b(for example,).

Please note that the thickness of the formed protective oil film does not depend on its strength. Thus, the mineral film is withstanding the load of about 900 kg per square centimeter, and the same film formed by modern synthetic oils based on the estrices can already withstand the load of 2200 kg per square centimeter. And this is with the same viscosity of oils.

What will happen if the viscosity is incorrect

In continuation of the previous topic, we list the possible troubles that may occur if the oil is selected in unsuitable for this viscosity. So, if it is too thick:

• The operating temperature of the engine will increase, as thermal energy will be discharged worse. However, when driving on low revolutions and / or in cold weather, it can be not considered a critical phenomenon.
• When driving on high speed and / or at high load on the engine, the temperature can significantly increase due to which there is a significant wear of both individual parts and the engine as a whole.
• The high temperature of the engine leads to accelerated oxidation of oil, which is why it is faster and loses its operational properties.

However, if you pour a very liquid oil into the engine, then problems may also arise. Among them:

• Oil protective film on the surface of the parts will be very thin. This means that the details do not receive proper protection against mechanical wear and exposure to high temperatures. Because of this, the details are faster.
• A large amount of lubricating fluid usually goes into a volunteer. That is, there will be a place.
• There is a risk of the so-called wedge of the engine, that is, his way out is in order. And this is very dangerous because it threatens complex and expensive repairs.

Therefore, to avoid such trouble, try to pick up the oil of that viscosity that the machine manufacturer allows the machine engine. By this, you will not only extend the life of its operation, but also provide the normal mode of its work in different modes.

Conclusion

Always follow the recommendations of the automaker and pour lubricating fluid with those values \u200b\u200bof dynamic and kinematic viscosity, which is directly indicated. Minor deviations are allowed only in rare and / or emergency cases. Well, the choice of one or another oil should be carried out by several parameters, not just viscosity.