Kinematic and dynamic viscosity oils

Viscosity (Viscosity).Viscosity is an internal friction or resistance of fluid flow. The viscosity of the oil, firstly, is an indicator of its lubricating properties, since the quality of lubrication depends on the viscosity of the oil, the distribution of the oil on the surfaces of the friction and, thereby wear out the parts. Secondly, the loss of energy depend on the engine and other aggregates. Viscosity is the main characteristic of the oil, by the magnitude of which is partially made the choice of oil for use in a particular case.

The viscosity of the oil depends on the chemical composition and structure of the compounds that make up the oil, and is the characteristic of the oil as a substance. In addition, the viscosity of the oil also depends on the external factors - temperature, pressure (load) and shift speed, therefore, the conditions for determining viscosity should always be indicated next to the numerical viscosity value.

The operating conditions of the engine determine the two main factors affecting the determination of viscosity - the temperature and speed of the shift.

The viscosity of the oil is determined at temperatures and shear speeds close to real during operation. If the oil should operate at low temperatures (even for a short time), at the same temperature, EGOs should also be defined. For example, all automobile oils intended for use in winter should be given low-temperature characteristics.

The viscosity of the oil is determined using two main types of viscometers (Viscometers):

• viscometers of expirationin which the kinematic viscosity is measured in the speed of free flow (flowing time). For this purpose applied capillary Viscometeror vessels with a calibrated hole at the bottom - englera Viscometers (Engler), Seibolt (Saybolt), Redwood (Redwood). Currently, a glass capillary viscometer is used for standard definitions; It is characterized by simplicity and accuracy of definition. The shear rate in such a viscomemetra is insignificant.
• rotary viscometeries (Rotational Viscometers),in which the dynamic viscosity of the torque with the installed rotor speed is determined or the rotor speed at a given torque.

Viscosity is characterized by two indicators - kinematic Viscosityand dynamic viscosity (Dynamic Viscosity).Dynamic viscosity measurement units: P - poise (R -Poise)or santipauzwed (cf \u003d mpa-s). Dynamic viscosity is usually determined by a rotary viscometer. Kinematic viscosity, due to dynamic viscosity to density (H / R). Cinematic viscosity measurement units - stock (St.— stoke)or santistoke (CST - CENTISTOKE,I CST \u003d 1 mm 2 / s). Numerical values \u200b\u200bof kinematic and dynamic viscosity are somewhat different, depending on the density of oils. For paraffin oils, kinematic viscosity at a temperature of 20 - 100 ° C exceeds a dynamic approximately 15-23%, and for naphthenic oils, this difference is 8 - 15%.

Kinematic viscosity It characterizes oil fluidity at normal and high temperatures. Methods for determining this viscosity are relatively simple and accurate. The standard device is currently considered a glass capillary viscometer, in which the time of oil expiration is measured at a fixed temperature. Standard temperatures are 40 and 100 ° C.

Relative viscosity Determined on the viscometers of the Saint, Redwood and Englera. These are vessels with a calibrated opening at the bottom, through which the exact number of oil flows. When measuring the flow time, the specified oil temperature in the viscometer should be maintained with the necessary accuracy. The universal viscosity of the SHIP, determined according to the ASTM D 88 standard, is expressed in universal Seconds SUS SAYBOLT UNIVERSAL SECONDS.This simplified method of determining kinematic viscosity is more widely used in the United States. In Europe more often enjoy seconds Redwood(Redwood Unit - Redwood Units)and degrees of Englera (E °, Engler Units).The degree of Englera is a number indicating how many times the viscosity of the oil exceeds the viscosity of the water at 20 ° C, so the enclosetter of the Englera must measure the time of water flow at 20 ° C.

Dynamic viscosity Usually determined by rotational viscometers. The viscometers of different designs imitate the real conditions for oil operation. Ultimate temperature and shear rate are usually allocated. The main methods for determining the viscosity of motor oils are provided by the SAE J300 APR97 specification. This specification sets the values \u200b\u200bof SAE viscosity degrees for motor oils and determines the procedure for measuring the necessary viscosity parameters. Standard methods for determining dynamic viscosity can be divided into two groups - low-temperature viscosity and high-temperature viscosity, determined under conditions close to the actual operating conditions of the engine.

Characteristics of low-temperature viscosity :

• providing cold engine launch (MaximumLow-Temperature Cranking Viscosity),determined by means cold Engine Run Simulator CCS (Coldcranking Simulator)(ASTM D 5293);
• maximum low-temperature viscosity, providing owl pumpingin engine (MaximumLow-Temperature Pumping),determined by means mini Rotational Viscometer MRV (Mini-RotaryViscometer)according to the ASTM D 4684 method;
• as additional information about low-temperature viscosity, can be determined boundary (limit) Pumping temperature by ASTM 3829. (Borderline Pumping Temperature) and viscosity at low temperature and low shift speed(Low Temperature, Low Shear Rate Viscosity),so-called tendency to jellying or gelling index GELATION INDEX.Determined on the scanning viscometer Brookfield according to the ASTM D 51 technique: (Scanning Brookfield Method);
• filterability Filteracty)motor oils at low temperatures show the tendency for solid paraffins or other inhomogeneities leading to clogging oil filter. Some influence on filtralability can have water in cold oil. The filterness of motor oil is determined by the standard "General Motors" GM 9099P "Test for the determination of filterness motor oil» Engine Oil Filterability Test-EFT)and is estimated as a reduction in flow in%.

High temperature viscosity characteristics:

• Kinematic viscositydetermined on a glass capillary viscometer at 100 ° C and a low shift rate (ASTM D 445).
• High temperature and high speed viscosity shift at Hhs. determined at a temperature of 150 ° C and the shift rate of 10 6 s -1 is determined: in America - with help conical Bearing Simulator TBS (TaperedBearing Simulator)(Fig. 2.36) according to the ASTM D 4683 technique, and in Europe - on viscome meter Ravenfieldor conical cork fuelsimilar design (Ravenfield Viscometer, Tapered-Plug Viscometer),according to the methods of Ses L-36-A-90 or ASTM D 4741;
• Stability to shift SHEAR STABILITY)- This is the ability of oil to maintain a stable viscosity with the continuous effects of high shift deformation. Determined: in Europe with bosch Injector Pump (Bosch Injector)through which the oil heated to 100 ° C is passed 30 times and the viscosity decrease (CE L-14-A-88) is measured, in America - also (ASTM D 6278) or in the CRC L-38 bench oil stand after 10 hour work (ASTM D 5119).

Consider some of the features of viscosity definition methods. Brookfield viscometer is a device for determining low-temperature viscosity at low shear rate. It is equipped with a set of rotors of different magnitudes and shapes. Speed \u200b\u200bcan be changed stepwise wide. During the change, the speed is supported constant. Torque is a measure of apparent viscosity. The distance between the stator and the rotor is relatively large, therefore it is believed that the shear rate is low and the walls of the viscometer vessel do not affect the value of viscosity, which in this case is calculated by the power of internal friction of oil and is called brookfield Viscosity Viscosity(in PA-C), or apparent viscosity (Apparent Viscosity).This method defines the apparent viscosity of automotive transmission oils at low temperatures (according to ASTM D 2983, SAEJ 306, DIN 51398).

Low-temperature engine launch viscosity (Low-Temperature CRANKING VISCOSITY)it is an indicator of oil ability to flow and lubricate friction nodes in a cold engine. It is determined by cold Cold CRANKING SIMULATOR launch simulator(DIN 51 377, ASTM D 2602). The CCS simulator is a rotary viscometer with a small distance between the profiled (non-cylindrical) rotor and the stator adjacent to it. Thus, the gaps in the engine bearings are simulated. Special engine A constant torque is maintained at a given temperatures, and the rotational speed is a viscosity measure. The viscometer is calibrated with the use of reference oil. Used to determine launch viscosity (CRANKING VISCOSITY)in centipools (SP) at different set temperatures, respectively, with the estimated degree of SAE viscosity for engine oil (-5 ° for SAE 25W; -10 ° for SAE 20W; -15 ° for SAE 15W; -20 ° for SAE 10W; -25 ° for SAE 5W and -30 ° C for SAE 0W).

Viscosity of pumping (Pumping Viscosity)it is a measure of oil ability to flow and create the necessary pressure in the lubrication system in the initial stage of the cold engine. The viscosity of the pumping is measured in centipuamas (SP \u003d MPa C) and is determined according to ASTM D 4684 on the MRV mini-rotational viscometer. This indicator is important for oils capable of geminating with slow cooling. Such a property most often have all-season mineral engine oils (SAE 5W-30, SAE 10W-30 and SAE 10W-40). When testing is determined either the stress of the shift required to destroy the jelly or viscosity in the absence of a shift voltage. The viscosity of the pumping is determined at different specified temperatures (from -15 ° for SAE 25W to -40 ° C for SAE 0W). Pumping is provided only for oils with a viscosity of not more than 60,000 MPA s. The smallest temperature in which the oil can pump out is called the lower pumping temperature, its value is close to the smallest temperature of operation.

Temperature dependence of viscosity at low temperature and shift voltage (Low Temperature, Low Shearrate, Viscosity / Temperature Dependentdetermined by the ASTM D 5133 method help scanning viscometer Brookfield (Scanning Brookfield Method).This indicator is necessary to evaluate the oil ability to enter the lubrication system and to the friction knots in the cold engine after the innovative stay at a low temperature. Before measuring the oil should be a specific cooling cycle, as well as in determining equilibrium temperature stretching (Stable Pour Point).Such a test takes a lot of time and is used mainly when developing new oil recipes.

Evaluation of oil filterness using the GM P9099 method is introduced in category SH, SJ and ILSAC GF-1, GF-2 for SAE 5W-30 and SAE 10W-30 oils. This method is developed by General Motors and is used by it since 1980. It imitates the procurement of the oil filter with a precipitate formed in the presence of water and condensate breaking crankcase gases during short-term operation after a long parking. The estimate is carried out according to a relative decrease in the flow rate through the filter with a sequential oil test and a mixture of water with water. The mixture is prepared by slow stirring in the amount of 30 s in a closed stirrer 49.7 g of oil, 0.3 g of deionized water and dry ice. After stirring, the mixture in the open vessel is kept in the furnace at a temperature of 70 ° C for 30 minutes. It is then cooled to 20 - 24 ° C and withstand at this temperature 48 - 50 hours. Reducing the flow rate should not be more than 50%.

Stability to the shift is the ability of oil to maintain a constant value of viscosity under the influence of high shift deformation during operation. With a rapid slide of friction surfaces, a high flow rate of oil in narrow gaps is achieved and a high shift deformation manifests itself, which causes the destruction of polymer molecules (thickeners) of the oil. Stability to shift deformation is an important indicator for oils used in modern high-speed, highly loaded, powerful and small engines. Oil ability to maintain a stable viscosity is determined by time during which the viscosity changes to a certain value. Sometimes use the indicator stability index sSI shift (ShearStability Index).It is determined by the ratio of the loss of viscosity of the effect of thickening with a polymer thickener, expressed in%. SSI is determined by different methods: in Europe use a diesel pump-nozzle of the Bosch design (Bosch Injector)(CEC L-14-A-88). In America, this indicator is determined by two methods - as in EVPONE (ASTM D 6278) or in the CRC L-benoline engine stand; After 10-hour work (ASTM D 5119).

With a relatively small shift deformation, polymer molecules are only unchecked, and after removing the voltage, over time, can restore their configuration and viscosity. That reducing viscositycalled tEMPORARY VISCOSITY LOSS - TVL)and sometimes it is observed when determining HHS viscosity on a rotary viscometer - a conical bearing simulator.

Pressure viscosity dependence

When pressure rises, we reduce the volume and the mutual attraction of molecules is enhanced and the flow resistance increases, the viscosity of the oil increases. With increasing temperature, the opposite process and the viscosity of the oil decreases.

At low temperature and high pressure, the viscosity of the oil in engagement gearsmay increase so much that the oil will become a solid plastic mass. This phenomenon has a certain positive effect, since the oil in a plastic state does not flow out of the gap of the conjugate surfaces and reduces the effect of shock loads on the part.

Viscosity characteristics

With increasing temperature, the viscosity of the oil is reduced. The nature of the viscosity change is expressed by parabola. This dependence is inconvenient to extrapolation for viscosity calculations. Therefore, the viscosity viscosity curve from temperature is built by semi-luguriform coordinates, in which this dependence acquires almost direct.

Visitiousness index VI (Viscosity Index) -this is an empirical, dimensionless indicator to assess the dependence of the viscosity of the oil from temperature. The higher the numerical value of the viscosity index, the smaller the viscosity of the oil depends on the temperature and the lower the slope of the curve.

The oil with a higher viscosity index has a better turnover at a low temperature (launch of a cold engine) and a higher viscosity at the engine operating temperature. The high viscosity index is necessary for all-season oils and some hydraulic oils (liquids). The viscosity index is determined (according to ASTM D 2270, DIN ISO 2909) with two reference oils. The viscosity of one of them is highly dependent on the temperature (the viscosity index is taken equal to zero, Vi \u003d 0), and the viscosity of the other - little depends on the temperature (the viscosity index is taken equal to 100 units, Vi \u003d 100) .. at a temperature of 100 ° C, the viscosity of both references. Oils and oil studied should be the same. The viscosity index scale is obtained by dividing the difference in the viscosity of reference oils at a temperature of 40 ° C per 100 equal parts. The viscosity index of the test oil is found on the scale after determining its viscosity at a temperature of 40 ° C, and if the viscosity index exceeds 100, it is found in the calculation.

The viscosity index depends on the molecular structure of the compounds constituting the basic mineral oils. The highest viscosity index happens in paraffin base oils (about 100), naphthenic oils are significantly lower (30 - 60), w.aromatic oils - even below zero. When cleaning the oils, their viscosity index is usually increasing, which is mainly due to the removal of aromatic compounds from oil. Hydrocracking oil has a high viscosity index. Hydrocracking is one of the main methods for producing oils with a high viscosity index. High viscosity index in synthetic base oils: in polyalphaolefins - up to 130, in polyethylene glycols - up to 150, in complex polyesters - about 150. The viscosity of the oil viscosity can be enhanced by the introduction of special additives - polymer thickeners.

Quite often, especially among novice car owners, the viscosity of the engine oil becomes the determining parameter when this is selected consumables. The decision is usually taken on the basis of the opinion of comrades: "I am 10W-40 (5W-40)", etc.

In fact, to correctly choose which oil to fill, it is important to know not only the necessary class of viscosity, but also the other characteristics that are not so much, but all of them are desirable to know if you decide to get it yourself.

What is the viscosity of motor oils

The main task of the engine oil is the lubrication of the conjugate parts, ensuring the maximum tightness of the engine cylinders and the removal of wear products.

Obviously, it is impossible to create a lubricant capable of maintaining the entire set set of operational properties in an indefinitely wide range of temperatures, which the engine of the car is very wide. In the frost, it will become more dense, with high temperatures, on the contrary, its fluidity increases sharply.

Do not assume that the temperature of the heated motor is stable. Temperature sensor, indications from which are derived dashboardIt displays only the temperature of the coolant, which, in fact, remains almost unchanged (about 90 degrees), thanks to the proper operation of the engine cooling system. The lubricant temperature changes significantly depending on the place, speed and intensity of circulation and can reach 140-150 degrees.

Considering this, automakers calculate the optimal characteristics of motor oils, which must ensure the maximum possible efficiency power aggregate With its minimum wear, in normal for this engine Operating conditions.

Since with a change in temperature, the viscosity changes, the Association of automotive engineers of the United States (SAE) developed and adopted by viscosity classification.

Kinematic and dynamic viscosity

It should be distinguished by such concepts as kinematic and dynamic viscosity. Kinematic characterizes the turnover of motor oil in conditions of normal and high temperatures. According to the generally accepted standard, it is measured at 40 and 100 degrees Celsius.

A kinematic viscosity is measured in centistoxes (CST or CST), or in capillary-viscose meters - in this case, kinematic viscosity reflects the time of leakage of a certain amount of oil from the vessel with a calibrated hole at the bottom (capillary viscometer) under the action of gravity.


Depending on the density of lubricant material, the kinematic and dynamic viscosity is numerically different from each other. If we are talking about paraffin oils, the kinematic is more by 16 - 22%, and in naphthenic oils this difference is where - from 9 to 15% in favor of kinematic.

The dynamic or absolute viscosity μ is the force that acts on the unit area of \u200b\u200bthe flat surface moving at a single velocity with a relatively different flat surface located at a single distance from the first.

In contrast to kinematic, dynamic does not depend on the density of the lubricant itself. A dynamic viscosity is determined using rotary viscometers that mimic the real conditions for the operation of motor oils.

How to choose a viscosity class by SAE

SAE classification is an international standard that determines the viscosity of motor oils. We should not forget that the SAE class does not decipher the quality characteristics of the oil, this index does not indicate the possibility of its application for a specific car model.

Viscosity according to the SAE standard has a digital or digital lettering, from which you can determine the seasonality of lubricant and temperature ambientat which it can be used.

For example, the SAE 0W - 20 class says that the All-season oil:

1. the letter W (from English Winter) indicates that it can be used in winter;
2. 0, which goes next, indicates the minimum permissible temperature of the motor startup to -40 degrees (from the number before W you need to take 40);
3. the figure 20 determines the high-temperature viscosity of the oil, it is quite difficult to translate to the language-minded to the ordinary car owner.

It can only be said that the higher the index value, the higher the viscosity of the oil at high temperatures. How these characteristics are suitable for this carcan only say the manufacturer.

Simply put, to choose the right SAE class, you need to know what values \u200b\u200bthere is an average temperature in the winter in the area where the machine is operated. If it does not fall on average below -25, then quite suitable oilhaving the SAE 10W - 40 index that is most common in stores. For the same reason, it is the most used.

For seasonal oils, the SAE classification has a shorter look:

• winter - SAE 0W, SAE 5W, etc.;
• summer is indicated simply by the two-digit number of SAE 30, SAE 40, SAE 50.

For more information about properties, the table contains below. Presented decoding the viscosity of motor oils using SAE classification. The first table contains information about the temperature ranges of oil operation, in a convenient, graphical format, and the second contains data on the numerical viscosity characteristics.




Often, novice car owners are mistaken, going to purchase oil for the gearbox. Come to the store, they are lost because the viscosity transmission Oil It has a completely different designation that does not have anything in common with the motor, and choosing it, it is necessary to be guided by completely different knowledge.

Another classification of motor oils

In addition to the classification by SAE, there is a classification of motor oils in quality. These characteristics defines the API or ACEA index. Index of PO aPI classification It is viewed for SA, SB, ..., SF gasoline engines (outdated engine oil classes), and further SG, SH, SJ, SL, SM - existing classes. The index for diesel engines instead of the letter S has in its composition Literon C. At the moment, the maximum valid class is CI-4 Plus. In stores canisters with an index below SG and CF find almost impossible.

Indexes in the ACEA classification are recorded differently. Lubricants for gasoline engines are indicated by A1, A2, etc. For diesel engines - B1, B2, ... Higher indices - A5 and B5.

Deciphering the quality characteristics of oils according to the API and ACEA specifications within this article will not be brought. This topic is highlighted in detail on specialized resources on the Internet, where both comparative data and numerous tables with measurements are given.

An important indicator Lubricating properties is the viscosity of the oil. It is determined by the chemical composition and structure of the compounds in the lubricant. In fact, it depends on this characteristic, to what extent is the liquid lubricates the surface of the filament of the power unit. Its properties are influenced by external factors, such as temperatures, load and shear rate. That is why the test conditions are indicated next to the specific value.

What is the kinematic and dynamic viscosity of the oil?

In order to understand the difference, let's consider their characteristics.
The kinematic viscosity of the engine oil, the unit of measurement of which MM2 / C (CST) shows its turnover at normal and high temperatures. To measure this indicator use glass viscometer. They flow the time for which the lubricant flows over the capillary at a given temperature. IN this case A low shear rate is used, and the kinematic viscosity of the oil is measured at 100 0.

Dynamic viscosity is measured by a rotary viscometer, which simulates the conditions as close as possible to real.

Methods that determine the viscosity of motor oil are pre-installed in the SAE J300 APR97 specification. Following precisely this certification, all lubricating fluids are divided into 3 types:
- Summer;
- winter;
- All-season.

If only numbers are used in the title, for example, SAE 30, SAE 50, etc., the data of the fluid belong to the summer motor lubricants. If the digit and letter w is used, for example, SAE 5W SAE 10W - winter lubricants. When there are 2 of these species in the designation of the class, this fluid is called the All-season.

Let's look below, which means the viscosity of the oil in SAE.
SAE classification (Association of automotive engineers) shares all oils by its ability to remain in liquid state (flow), and it is good to lubricate all the parts of the power unit at different temperature indicators.

The above temperature indicators are given, depending on the value that determines the viscosity of the engine oil. The table shows at what temperature indicators of the fluidity of a particular fluid will not lose its lubricating properties.

Why when replacing the lubricant fluid, you need to take into account the viscosity of the oil and what do the numbers mean?

A simple example for clarity. As you know, the low viscosity of the oils for engines contributes to their normal operation in winter (SAE 0W, 5W). If the fluidity is low, respectively, the oil film covering the part of the power unit will be fine. The manufacturer in the technical manual specifies the valid values, as well as tolerances for each engine type. If you fill with high yield lubricants, the motor will work with a load at elevated temperature. This sharply reduces its motor life.

And now, on the contrary. You pour fluid with fluidity below designated level. In this case, during operation, the lubricant breaks occur, and the motor can jam. The viscosity of the oil depending on temperature. No need to think that the bay in the "Super Lubricant" engine, which is used on sports carsYour car will start to "fly." It is necessary to pour the liquid that the manufacturer recommends.
Another error is that some motorists do not distinguish the type lubricants From their fluidity. For example, the viscosity of synthetic oils can be the same as mineral or semi-synthetic. In this case, they differ in composition, and not physical properties.

What is the viscosity of the oil to choose for the engine of your car.

First of all you need to see in technical guide. The manufacturer indicates a manual, what oil viscosity is better suitable for the engine to ensure its durable work. If there is no possibility to watch the recommended viscosity of the oil, then it is important to identify several points:

• at what minimum and maximum temperature your car will be operated;
• whether the load will be used (trailer, additional cargo or off-road ride);
• what is the condition of the engine (new or ex-in operation).

Following these indicators, you must pick up that viscosity car Oilwhich will ideally lubricate the details of the power unit.

A few words about other types of lubricants

Transmission fluids

Transmission fluids correspond to the SAE J306 classification. The viscosity of the transmission oil depends on the temperature conditions of operation. As well as motor transmission fluids Conditionally divide on:

• winter (SAE 70W, 75W, 80W, 85W);
• summer (SAE 80, 85, 90, 140, 250);
• combined (for example, SAE 75W-85).

To understand what lubricant to use in the box of your car, you need to watch the recommendations and tolerances of the manufacturer of the CAT.

Hydraulic lubricants

In addition to its main function - pressure transmission, hydraulic fluids perform lubricating parts of hydraulic pumps. Based on this, they are divided into classes. Viscosity hydraulic oil Itself low, medium and high. Below is a table that shows the possible classes of hydraulic lubricants.

The viscosity of the engine oil is one of the main parameters on which it is determined whether a specific car is suitable under conditions of a specific temperature range. But by no means always the point of view of different people on this score are the same. So it is much easier to figure it out in everything yourself and decide what fluid to pour and why.

Engine oil lubricates all running parts of the mechanism

What is called viscosity?

The viscosity of the engine oil is its ability to maintain its turnover, being between the internal parts of the car engine. Automotive motor grease Performs a very important function - it lubricates the internal parts of the engine, not allowing them to rub on each other "on dry", and also provides minimal strength of friction between them. It is impossible to create such a lubricant that would not have changed its characteristics when increasing or decrease in the engine temperature. Viscosity performance will vary significantly when driving, since the temperature variation between the internal parts of the engine is very high and can reach 140-150 degrees Celsius.

Automakers are selected and determined for each optimal oil fluidity, in which the efficiency will be maximized, and the engine wear, on the contrary, is minimal. That is why it is better to choose the lubricant that is recommended by the car manufacturer for a specific model, and not the one that comes friends or even specialists from the car service.

Dynamic and kinematic oil viscosity

The kinematic viscosity of the oil determines the characteristics motor fluid at normal and high temperatures. As a rule, the normal temperature is considered 40 degrees Celsius, high - 100 degrees. Cinematic viscosity is measured in centistoxes. In addition, this value can be measured in capillary-viscometers - in this case, the leakage of a certain amount of lubrication through the hole at the bottom of the tank during a certain period of time is determined.

Dynamic (absolute) viscosity in no way depends on the density of the substance itself and determines the resistance arising when moving at a certain speed of layers of oil located on a short distance. A dynamic viscosity is measured using an apparatus that imitates the operation of the engine fluid in real conditions - rotary viscometers.

How to choose a viscosity?

In order to somehow classify lubricants, as well as facilitate the search for motor fluid with the desired characteristics, an international SAE standard was introduced.
SAE is an oil viscosity index, it must be indicated on the canister label. But it is important to know that the viscosity of the SAE oil in any way defines the quality of the lubricant or its compatibility with the exact engine. Other indexes are responsible for this, also specified on the canister label.

SAE may have a digital or digital-screen designation, it depends on what type of climate is suitable for lubricant. There are three kinds of seasonality:

• summer (designated as SAE 20, SAE 30);
• winter (SAE 20W, SAE 10W);
• all-season (here the marking is already "hybrid" - SAE 10W-40, SAE 20W-50).

All winter engine fluids have the letter W in the SAE index, which means Winter (winter). To find out at what minimum temperature your car will start with a defined engine fluid, you need to take 40 from the number going to the letter W. That is, if your lubricant has the Sae 10W index, then you can safely start at temperatures in minus thirty Celsius.

The numbers in the SAE index that indicate the "summer" component of the viscosity of the lubricant, that is, the numbers after W, quite difficult to translate to the tongue-minded man. You can only say that the more these numbers, the more viscous there will be fluid at high temperature values. To find out whether the summer or all-season oil is suitable for your viscosity motor, you need to use the viscosity table of engine oils. However, do not forget that the most faithful source of information about how the viscosity of the oil is better - this is your car documentation or in extreme case consultation in the official dealer Center from the manufacturer.

What is worse - understated or inflated viscosity?

What will happen if the oil viscosity on the low temperature will be higher than the norm? The friction force increases. The engine temperature as a result will increase and stop only when the viscosity falls to the required norm (and therefore the friction force will decrease). On the one hand, nothing bad will happen, but the engine will operate at a higher temperature, not calculated by manufacturers. And this can badly affect its resource - the details will become faster. That is, the likelihood of engine breakdown increases. And besides this, the engine fluid will have to change more often, since it is rapidly spent due to the high temperature.

It is much worse and more dangerous when the viscosity of the lubricant is lower than is required. As a result, lubrication consumption will increase significantly, and there is also a possibility that the motor will simply embar high revolutions. That is why it is strongly recommended to choose motor fluids that have an automaker tolerance.

Synthetic, semi-synthetic, mineral water - which oil is better?

Mineral oil is a motor fluid, created from petroleum products. As a result, this type of oil is divided into oil and paraffin. They have a certain fluidity, as well as strict temperature regime, so that it is possible to change these parameters using additives (because of which, by the way, the liquid is quickly coming into disrepair).

Synthetic oil is a more versatile analogue of mineral, as synthetic is a product of the synthesis of certain chemical elements, and changing its parameters, you can achieve almost any viscosity that is in demand in the car liquids market.

Semi synthetic oil - hybrid synthetics and mineral water. It has many advantages both synthetic and mineral lubricant, but choose the optimal for concrete Engine Sometimes it happens very difficult.

A significant difference between the three types of oils occurs only in winter, when synthetics greatly wins. Due to its chemical structure, synthetic oil has good fluidity at low temperatures, and also stabilizes the operation of the engine. And besides this, it is almost not afraid of oxidation and much longer "exhaled."

Oil classification by other parameters

In addition to the SAE index, there are other indices that classify motor fluids by quality classes. For example, standard API Provides two letters of the Latin alphabet, the first letter - either s (for gasoline engine), either with (for diesel). The second letter is directly the quality class itself. What it is further in the alphabet, the later this standard was developed, and as a result, the higher the quality of the engine fluid. For gasoline engines, the highest quality class is SM. For diesel - CL-4 Plus.

In Standa ACEA classes Quality is recorded differently: with A1 on A5 for gasoline engines and with B1 for B5 for diesel. By the way, A5 and B5 by the ACEA classification have a very low viscosity, so they are suitable only for certain types of engines, so be careful with their operation.

Conclusion

The best engine fluid is the one that will fully comply with the instructions of the automaker and the requirements of your car. It is necessary to approach the selection of a motor fluid and correctly. Pay attention to the manufacturer, expiration date, type and classification - it will save the engine, will extend the service life. But it is best to look for those oils that are specified in the documentation for specific model Car as recommended, and no matter how old the car, how many thousands of kilometers you travel and what "authoritative" opinions advise.

Motor oil classes

• winter "w"
• summer
• all-season

Whistling

Pummier

Kinematic viscosity

Dynamic viscosity HHS

You will be interested

Your question has been sent successfully. Thank you!

Close

SPECIFICATION OF MOTOR OILS FOR SAE (by viscosity)

SAE (Society of Automotive Engineers - Society of automotive engineers). SAE Specification J300 is an international standard for the classification of motor oils.

Oil viscosity - the most important characteristic Motor oil, determining the ability of oil to provide stable work Engine, both in frost (cold start) and hot weather (at maximum load).

The temperature indicators of the engine oil are based on two main values: a kinematic viscosity (ease of oil yields at a given temperature under the influence of gravity) and dynamic viscosity (shows the dependence of changes in the viscosity of the oil from the speed of moving parts relative to each other). The higher the speed, the lower the viscosity, the lower the speed, the higher the viscosity.

Motor oil classes

• winter "w" - Winter-Winter (SAE 0W, 5W, 10W, 15W, 20W, 25W). These engine oils are characterized by a low viscosity, provide a safe cold start at temperatures below zero, but do not provide enough good lubrication in the summer.
• summer (SAE 20, 30, 40, 50, 60). Oils of this class are characterized by high viscosity.
• all-season (SAE 0W-20, 0W-30, 0W-60, 5W-20, 5W-30, 5W-40, 5W-50, 5W-60, 10W-20, 10W-30, 10W-40, 10W-50, 10W-60, 15W-30, 15W-40, 15W-50, 15W-60, 20W-30, 20W-40, 20W-50, 20W-60). Combines simultaneously characteristics of summer and winter engine oil.

Viscosity properties at given low temperatures

Whistlingdetermine using a cold starter simulator (Cold Scroll from Starter) CCS (Cold Cranking Simulator). The rate of dynamic viscosity of oil and temperature in which oil has sufficient fluidity capable of ensuring a safe engine start.

Pummierdetermine, referring to the readings of the MRV mini-rotary viscometer (Mini-Rotary Viscomeer) - by 5CO below. The ability to pump oil pump in the engine over the lubrication system, eliminating the possibility of dry friction of parts.

Viscosity properties at given high temperatures

Kinematic viscosity At a temperature of 100 degrees Celsius. Shows the minimum and maximum viscosity values \u200b\u200bof the engine oil under the condition of a heated engine.

Dynamic viscosity HHS (High Temperature High Shear) at 150 degrees Celsius, and shift speed 106 C-1. Determines the properties of engine oil by energy saving. The stability indicator of viscosity characteristics at extreme temperatures.