Automobile oil is an indispensable assistant for any motorist. It provides lubrication of mechanisms rubbing together, smoothing surfaces, as well as removing excess debris that occurs when parts interact with each other.
A lot depends on the right choice of lubricants. Firstly, the quality of the selected oils further determines the wear resistance of automotive parts. In addition, the characteristics of the purchased oil determine the ability to function under various temperature conditions. Thirdly, the use of low-quality products entails an increase in the gaps between the interacting mechanisms, which is accompanied by an increase in fuel consumption, wear of expensive parts and mechanisms, and a number of other serious problems.
Viscosity as one of the key parameters of engine oil
The choice of motor oils is determined by various parameters. But for many buyers, the key parameter is the viscosity of the lubricant. Thanks to this parameter, automotive oil lingers longer on the surface of the engine, and is correctly distributed between the rubbing parts.
Basic viscosity parameters
When analyzing the information that manufacturers declare on product labels, each buyer should distinguish between concepts such as kinematic and dynamic viscosity. They differ in density, units and methods of measurement and are used for indicators of different classes of lubricants.
Kinematic viscosity indicates such a property of the oil as its fluidity. It is determined at normal and maximum operating temperatures. Usually, modes such as forty and one hundred degrees Celsius are chosen for testing. This value is measured in centistokes.
Based on the kinematic viscosity, the viscosity index of the engine oil is calculated. If you want to choose the really best lubricant, the index should be more than 200; multigrade oils usually have it.
Dynamic viscosity characterizes the resistance force when liquids move relative to each other, regardless of density. The unit of measure is centipoise.
International standard that regulates the viscosity of oils
To date, the most popular classification of lubricants is SAE. This specification is recognized as the only international standard on the basis of which the viscosity of the oil is calculated based on the temperature regime of the medium.
Society of Automotive Engineers is an acronym for the Society of Automotive Engineers of the United States of America.
The viscosity of the engine oil according to SAE must meet the following conditions:
- pumpability - due to this property, under conditions of minimum temperatures, quick access of oil to the oil receiver is ensured;
- crankability - helps to increase starting properties, provides the necessary resistance and achievement of starting speed in cold weather;
- the most effective viscosity in hot conditions;
- kinematic viscosity - determines the viscosity class of motor oils.
The SAE specification is used when determining the viscosity level of a lubricant, the requirements for oils are taken into account when releasing new products, as well as for research and detailed study of old and new formulations.
Types of oils depending on the temperature regime
The viscosity of lubricants can vary under different conditions. It is directly dependent on the ambient temperature, on the rate of heating of the mechanisms, on the mode of operation of the engine. At low temperatures, the viscosity should not be too high to ensure the vehicle starts in cold weather. In high temperature conditions, on the contrary, the lubricant helps to ensure proper pressure and creates a protective layer between the surfaces that are in contact.
In terms of viscosity, lubricants are divided into winter, summer and all-weather. All-weather products are more convenient. It is more energy efficient, and these oils do not need to be changed as often as materials for a particular season.
Operating temperature ranges for different SAE oils
The table clearly shows at what temperatures different types of lubricants can be used.
The table of viscosity of engine oils by temperature is presented below.
The engine oil viscosity table has numeric and alphanumeric designations, thanks to which the seasonality of the oil and the ambient temperature are determined.
winter oils
As an example, consider the viscosity of 5w30 engine oil. The decoding of the viscosity of engine oil for winter oils is as follows.
For winter oils, an international designation with the letter “w” has been created. When calculating, 40 must be subtracted from the figure in front of it, as a result, we obtain the temperature regime at which lubricant can be used. To find out the cranking temperature of the engine, you need to subtract 35.
Above is a table of engine oil viscosity by temperature. Winter oils are in its upper part.
Winter lubricants are suitable for use under the following temperature conditions:
- 0W - recommended for use in frosts down to -35-30 o C;
- 5W - recommended for use in frosts down to -30-25 o C;
- 10W - recommended for use in frosts down to -25-20 o C;
- 15W - oil is recommended for use in frosts down to -20-15 o C;
- 20W - oil is recommended for use in frosts down to -15-10 o C.
As already mentioned, the viscosity of winter oils must also meet the requirements for crankability, pumpability (should not exceed sixty thousand centipoise) and have the necessary kinetic viscosity.
The table of viscosity of engine oils for cold conditions is presented below.
Summer types of lubricants
Summer production is designated, according to the standard, only with numbers (for example, SAE 30) and means an average parameter indicating the viscosity of the material in working conditions at elevated temperatures.
The motor oil viscosity table for the summer season is as follows.
Multigrade oils
All-weather lubricants are applicable under various thermal conditions. Depending on the season, the viscosity can change and provide proper lubrication of the car's mechanisms. Thus, oils for all seasons meet the criteria for the highest cranking viscosity in cold weather, and the lowest in hot weather.
They are presented at the bottom of the viscosity-by-temperature table and consist of a combination of summer and winter oils.
The decoding is as follows: let's say the viscosity of engine oil is 5W-30: the viscosity grade "5W" allows the use of oil in the cold season, shows how easy it is to start the engine at low temperatures; "30" - indicates the summer class, using this indicator you can calculate the possibility of working at high temperatures.
The choice of engine oil by its viscosity
How to determine the viscosity of engine oil? This may be suggested by the manufacturer's recommendations. The structural features of the engine, its load on lubricants, the level of resistance, the degree of wear of the oil pump, the degree of possible heating of the oil under different operating modes in all places of the motor are taken into account.
When choosing the viscosity of the material for the winter season, you need to take into account the average temperatures of the region of residence. Choosing the right oil will help your car cope with cold starts, which cause additional friction and wear on parts. The engine oil viscosity table will help you navigate the large selection. Manufacturers recommend using SAE 0W among winter oils.
When choosing summer oil, you need to take into account the fact that parts can overheat especially in the hot season, airflow may be insufficient, so the oil must be viscous.
Conclusion
Manufacturers offer a fairly large selection of lubricants. The main characteristic of which is their viscosity. And it, in turn, directly depends on the temperature regime.
Even in very moderate climatic conditions, the temperature difference between the engine and its parts can reach two hundred degrees. The international SAE standard offers a choice of oils for different seasons. Universal oil - all-weather. But as the experience of motorists shows, with too much difference in temperature conditions, great frosts and too hot summers, all-weather lubricants are far from the best.
When choosing a viscosity grade of a lubricant for a personal car, it is necessary to be guided by the following criteria:
- structural features of the car and motor;
- the degree of corrosion of parts, the level of deterioration of the engine;
- basic modes of operation of the motor;
- temperature in different seasons across the region.
Due to such a parameter as viscosity, automobile oil can linger on the surface of the engine longer, be properly distributed between rubbing parts, preventing drying out.
The introduction of an exhaust gas recirculation system has led to new requirements for engine oils.
Recirculation - the supply of part of the exhaust gas back to the engine - made it possible to reduce the content of nitrogen oxides in the exhaust gas. However, due to recirculation, the temperature of the crankcase oil increased, on average from 120 to 130°C. Therefore, engine oil must have enhanced antioxidant properties. Otherwise, with a decrease in nitrogen oxides, soot emissions will increase. The solution was found in the form of ashless additives based on nitrogen and manich bases. Their use made it possible to maintain the required amount of metal-containing additives without harm to exhaust gas cleaning systems.
Extremely important indicators of the quality of engine oil are its sulfate ash content and high temperature shear viscosity. .
Sulphate ash content - This is an indicator that determines the amount of metal-containing additives in the oil. The more such additives, the higher the ash content. However, an excess, as well as an insufficient amount of additives, harms engine oil, as it becomes a source of additional low-temperature deposits on the engine: sludge, tar, coke. Today, in the production of motor oils, there is a clear trend towards a decrease in sulfate ash content - below 1.5%. In the meantime, most modern cars use low-sulphur fuels.
The ash content, as well as sulfur and phosphorus contained in the exhaust gases (EG), severely disable the exhaust gas converter, clog the cells of the particulate filters. SAPS oils were developed to solve this problem. In this abbreviation, the letters indicate the limitation in the oil of sulfated ash (Sulphated Ash), phosphorus (Phosphorus) and sulfur (Sulphur). The use of SAPS oils makes it possible to increase the service life of cleaning and neutralization systems up to 100,000 kilometers. This is especially important due to the fact that a catalyst containing expensive metals (platinum, ruthenium, palladium) is not cheap.
As you know, the main wear is on the cylinder-piston group and the crankshaft. The CPG accounts for 60% of wear, the crankshaft - 40%. That is why another fundamentally important indicator of oil quality is HTHS, or high temperature shear viscosity. In the engine, this oil parameter is essentially similar to the operation of crankshaft bearings. HTHS is measured in mipascals per second.
Today, there is a trend towards lower shear viscosity from the usual value of 3.5 mP/s. If the engine oil has a reduced HTHS, it can only be used in new engines prepared for this. The use of low HTHS oils in engines not designed for this purpose can lead to accelerated engine wear. It is explained simply. In engines adapted for low HTHS oil, the distance between the friction surfaces is extremely reduced, the parts fit so tightly that the gap is minimal. If the precision pairs of the traditional sample (i.e. the gap is greater than necessary), the oil film breaks and metal-to-metal contact occurs. Currently, low HTHS oils are used in a number of VW models, as well as on some BMW and MB models. This contributes to additional fuel economy. However, in most modern models, oils with a standard HTHS value are still used.
In the modern world, there is an increasing tightening of environmental standards, since cars account for up to 60% of all harmful emissions into the atmosphere. Automobile exhaust contains up to 200 chemical compounds, the most harmful of which are carbon monoxide, hydrocarbon compounds, sulfur, phosphorus and, finally, particulate matter, i.e. soot. Soot is produced mainly by heavy diesel engines. Formally, this is pure carbon, which, it would seem, is not dangerous for the environment. But when exhausting gases, it acts as an absorbent of harmful compounds: absorbing them, it accumulates carcinogens.
About 40 years ago, in world practice, the so-called. "multi-grade" oils are oils with a pronounced all-weather factor. Bases are used there "easier" - synthetic, more fluid ...Here from excessive liquefaction at operating temperatures, they are being caught up with polymeric thickeners. A noticeable qualitative difference between such oils and purely "summer" counterparts is a fair amount of polymer thickening. Flow characteristics pumpability such liquids somewhat lose their "linearity" depending on temperature, acquire, so to speak, a certain unpredictability ...
Concerned about this insignificant non-existent problem, the progressive oil-professional community began to fence inventing a new criterion for HTHS - "high-temperature shear viscosity". From the name it follows that this is a kind of "dynamic" criterion, more specialized than the high-speed outflow of oil through the capillary ... Why?
Not all liquids flow the same way, oil professionals said, and they stopped pouring oil in bottles and began to invent and standardize (*) criteria for the fluidity of liquids, tied to certain dynamic processes ...
***Pay special attention: low temperature the properties of modern oils have long been normalized only in dynamics. At the very least, but with the help of installations where they give a load to cold oil and try to imitate something there:
Unbelievable but true: Homegrown bottled oil dispensers are fiercely compliant with HTHS: that is, they do not trust the free flow of liquid at high temperatures. They look reverently at the numbers of "dynamic tests" of hot oil. Let us suppose. But at the same time (!), they do exactly the opposite with low-temperature viscosity: they spit on standardized dynamic methods, starting to do what ASTM / SAE and others have long abandoned (or maybe even never tried at all) - even it dawned on them that stupidly drain the frozen oil into the capillary, if there is an inevitable supply of it by the oil pump.
Not only stupid, but also stupid - there is no such dynamics in the engine. There are no gravity lubrication dynamics - but there is a whole oil pump, which in cold weather can pump up to 18 bar. Paradoxically, once again I observe double standards. Just now you said that you do not trust the "A" method, preferring the "B" method, but you immediately use this method where it obviously does not work. Moreover: it is precisely those who invented both of these methods that tell you about it!
If someone can explain what the logic is here, do not be silent.
Well, let's finish the lyrical stupidity ... remember how the attempt to standardize HTHS ended (attempts to evaluate the dynamics of oil at high temperatures) ...
And how it ended is even written on Wikipedia, and this could be the end of the article:
A 1989 American Society for Testing and Materials (ASTM) report stated that its 12-year effort to come up with a new high-temperature, high-shear (HTHS) standard was not successful. Referring to SAE J300, the basis for current grading standards, the report stated:
For 12 years(!) recognized senseless activities, these same professionals, led to a lack of results.
On this, they should also finish ...
But it seems that there is no place for logic here again: the parameter anyway (out of spite, so that the good does not disappear?!) enshrined in the SAE J300 viscosity standard. Fixed "minimum" HTHS for each viscosity class... HTHS was originally created as a replacement for the outdated standard - to meet the needs of new realities. He should have been replace, and was, for obvious meaninglessness, simply left in the standard complementary and ... closing - only as a rejection criterion! Instead of a replacement - a meaningless addition.
And you know what's the most fun?! So that's how they start using this "bottom" rejection criterion.
SAE normalizes the viscosity of the capillary flow in a fairly wide range. Look at the plate - for the common SAE40, this is almost exactly plus or minus 15%. From 12.5 to 16.3 cSt is a wide, 30% tolerance band. For this range minimum on "dynamic" viscosity - HTHS. Well, it would seem - range and range, minimum and minimum. One insignificant parameter does not interfere with another, unnecessary one. But the real magic begins when the professional again takes up his favorite kunstuk: he begins to choose the best of the standard.
Again there is a bloody harvest in the field of tolerance. As long as everything is in order, there are no problems. But our homegrown lovers start to choose the most standard nuts for most standard bolts. From there, the unseen begins: oils are ranked by HTHS... within the whole tolerance field of viscosity according to S.A.E.
Here, for example, for SAE 10W40 oils, impressive: 
I'll just draw a red line where the standard itself asks: 
Wild inconsistency! When there is such a difference between the standard and real results, you need to fire the rater. Why do we need a "norm" that can be fulfilled without doing anything at all ?! Just being butter...
It's even funnier when you're looking for record-breaking minimum rates in one way only you know: choose the maximum HTHS value in the SAE viscosity tolerance box.
Representing a professional looking for oil thicker, but not just, but to according to the standard SAE40... but thicker! The SAE40 standard can have oils from 12.5 to 16.3 cSt. Nobody bothers (since your engine is prescribed, as you think, "strictly SAE40") to look for SAE40 oil, but thicker - let me have SAE40 standard oil, but with a viscosity of 16 cSt! Funny? But above, what is it then? It's even worse here: the search for the "best oil" is carried out not according to a really existing range, but worse than that - according to a rejection parameter!
HTHS - rated minimum for a whole family of "capillary" viscosities. The task of the rejection criterion is only to set the lower bar.
I was not too lazy, I made a table from a wide range of different oils of different recipes and viscosities. The color gradient shows the trend and it's obscenely boring - the more... the more: 
From this standard itself with the indicated minimums, the ears of the viscosity dependence stick out -the higher the high temperature viscosity, the higher the rated HTHS value...
Well, what kind of argument is this when there are obvious inconsistencies in the table - the actual values of the parameters are sometimes barely out of the general range. Sometimes the viscosity is chu-u-u-dot lower than the neighbor, and HTHS is a little higher. Victory: this is the same, "non-Newtonian" manifestation - there are some recipes with a barely non-linear dependence.
There is only a little left: to prove what the ASTM group of scientists failed to do in 12 years: at least some connection of the parameter taken from the lantern with at least (!) With some kind of rejection criterion for the state of the engine.
I don't even know how. If you want to annoy a professional, ask him if he knows any fact that proves the advantage of SAE30 oil over oil, for example, SAE40 within one engine. No, I haven’t heard, the professional answers and will go to choose oils with higher HTHS ...
Tell me, how exactly and what high technologies are leading results achieved? What efforts are made by manufacturers (and what prevents the rest?!) to achieve such an impressive advantage over competitors within the standard (?).
Are you unhappy with the standard oil viscosity that you are looking for it density?
You say that you need "higher" HTHS - well, what's stopping you from pouring just "thicker" oil? If the SAE40 with the best in class HTHS has an impressive 4.5 units, then how much better would any 6, or even as many as 7 units! Please, give a link to the methodology (yes, at least to the favorite measurement of wear in working out), where 4 HTHS units would take precedence over oil with HTHS units, so in 2. At least in something!
It's amazing, but "normalizing the viscosity for the engine", confidently stating that only "SAE40" is suitable for your engine, the prescription tolerance for various all-weather oils according to HTHS turns out to be unexpectedly wide - under 30%! And it's even reflected in the standard:
I humbly ask any oil professional to explain to me one single fact: why is it that some SAE40 oils are allowed (sic!) to have more HTHS and another less? It is interesting that these "bigger" and "smaller" jumps from standard to standard among SAE engineers.
The viscosity of SAE40 turned out to be special - it is a "medium viscosity", where a variety of oils are found from 0W40, to 25W40, and even just "SAE40". It is obvious that oils with a smaller amount of thickener are "squeezed" more strictly - a kind of game of suppression for the second group of "magpies". This is not the first situation when not the product is brought up to the standard, but the labored "standard" emphasizes the properties of the product.
Emphasizes below. At the level of the plinth, we are shown the minimum height for hanging the chandelier.
Zebra?! - Only in stripes! - Elephant? - Exclusively with a trunk! And God forbid if the zoo is not built to our strictest standard! All commercial oils with an amazing margin fit into the "strictest" tolerances.
Pay attention to what severe restrictions await thickened grades SAE50 / 60. Them strictly it is forbidden to be non-HTHS higher than SAE40! Along with this, "thin" oils of the SAE30 type are ordered to be as resistant to dilution as part of the SAE40 oils. But we understand that this is just the opposite: parts of SAE40 oils are allowed to be the same as SAE30 ...
In general, you try to find at least one real oil that would balance at least on the verge of the standard. As you start looking, you will immediately notice: the lower the viscosity, the closer to the pro-threshold HTHS. It is logical: the numbers themselves are not rubber - SAE20 has a threshold of only HTHS 2.6. With the advent of innovative oils such as "SAE12" and even "SAE8", "HTHS 1" dawned on the horizon - you can't really go around lowering it. Do not invent negative values.
It is enough to take the real parameters of a single product line to see that the dependence is simply linear, almost proportional to the "heaviness" of the base oils. And only at the upper limit begins a slight "non-Newtonian" deviation in view of the overwhelming amount of thickener. But the "deviation" is with the same margin from the "minimum", which becomes embarrassing for the "standard".
HTHS is a completely artificial neoplasm aimed at emulating non-existent conditions, indistinctly normalized by absurd figures, with a threshold that is obviously surmountable by all market participants. This is a normal practice for oil professionals. Worse, the parameter is actually completely and linearly dependent on high temperature viscosity and is "glued" to the actual viscosity of an average oil with "Newtonian" characteristics - without significant thickener content.
But if suddenly, someone needed an indulgence - it's okay! - the standard rate suddenly drops by 30%, as in the case of SAE40 wide-range oils ... and the tolerance rate becomes equal to "SAE30" ... That is, we do not pull the technology "up", but lower the rate "down". It would seem that chemmotologists must furiously solve the problem of bringing wide-range oils of the SAE 0W40 standard to less versatile oils. Instead, due to the obvious lack of "technology", such oils simply drop the standard bar by 30%!
Imagine that you finally proved that HTHS is at least something, which means that you absolutely need your complex SAE 0W40 oil to be similar to a simple SAE40 summer oil. Since (and this is not news) there are no real chemical miracles for this, we simply prescribe in the standard that SAE 0W40 has the right to be the same in HTHS as SAE30 oil ... And so on, like this, many times already met oil professional miracles.
A funny and obvious conclusion, which, by the way, is unknown to absolutely all lovers of high oil technologies: HTHS is not an attempt to raise and improve something. By definition, this is just an attempt to keep the quality of modern multigrade oils at the level of antediluvian mineral water, in which there was almost no polymer thickener. You should at least read the standard carefully: 
Did you think that HTHS even not specified for cheap oils due to the fact that they have nothing to do with such a snout among newfangled synthetics ?! Like where is the shameful mineral "Lukoil" for 100 rubles a liter before a newfangled synthetic mobile phone ?! Nothing like that: there are no problems with HTHS for mineral oils at all - HTHS itself is just an attempt to bring the dynamic viscosity characteristics of oils with a thickener to the "mineral standard".
Once again, I would like to draw your attention: not only does there not exist a known dependence of the condition of the engine on the HTHS value, but there is at least no proven dependence of the condition of the engine on the viscosity of the oil used in it! And much worse than that - there are no recognized (standardized) methods for determining such a dependence. But we have heaps of "parameters" and "tests" ...
What is HTHS?
There are many answers. The most correct is nothing. A little more: a parameter that is designed to characterize the "nonlinearity" of the fluidity of oils with a polymer thickener present in them. An attempt to "pull up" modern all-weather oils such as 0W40 to "mineral" (!) Viscosity standards. Some modern oils contain too much thickener and may lose some of their viscosity. Hence all the fuss.
Should I choose oil according to HTHS?
Approximately with the same motive as looking for a thicker oil from the range of standard SAE viscosities. But to do this is even more sophisticated - according to the minimum rejection criterion.
As they suggested, this is exactly what "Mercedes" with MB229.5 approval is doing - it is looking for SAE30 thicker, but more HTTPS. All SAE30 oils with this approval have [email protected] around 12 and up. It's almost like SAE40 oils in a SAE30 canister! If it seems like a joke, you can check it out for yourself...
Why are mineral oils and many cheap oils not listed as HTHS? Only cool synthetics can boast good results?
If your neighbor is forced to report to the police every month, this does not mean at all that he is an honorary citizen of the city with special honors, and you are somehow worse than him, since you have been bypassed with such attention. HTHS is stamped only with oils of the "prone to runaway" category. Even the oil manufacturer himself, as it were, scores on such an important parameter, to which the standard obliges him (!) It is clear to the manufacturer: for such oils, it is guaranteed to exceed the tolerance - there is little (less) thickener there. Did you think...
Why is such an important parameter, which is present even in the main standard, not standardized when analyzing used oil?!
Yes, it's funny: the thickener can be destroyed under certain operating conditions. HTHS - fall. But no one even attempts to measure HTHS in laboratories.
If mining thickened normally at the end of operation, HTHS probably even increased. And if the thickener has collapsed, then it is enough to control the usual viscosity - the destruction of the thickener brings the oil closer to its base viscosity. Here, even the laboratory assistant understands: HTHS is not needed at all, even in the laboratory. It would be nice to concentrate efforts in the struggle for the creation of a thickener resistant to everything ... But this is a separate issue.
Why are real HTHS values so close to the rejection threshold for low viscosity oils? Does this mean that there is a scientific battle right at the forefront of progress?!
The formulations of such oils contain almost no thickener - it is impossible to make unthickened oils "non-Newtonian". You can limit the HTHS of such oils only by adjusting the numbers to their real characteristics. What is happening. As soon as you show SAE20 oil with HTHS like SAE40, or at least 30, we'll talk about the "science battle". That's why, tell me, for some reason there is still no SAE 0W20 oil with HTHS, say, 4 units? Too far from the requirements of the standard, difficult to do? Then why does HTHS SAE60, for example, exceed the "requirements" of the standard almost twice? What succeeded there, what "failed" for SAE20?))))
Well, why does the standard spare oils of thick standards like SAE50 / SAE60 so much? The requirements for them are similar to SAE40 oils!
The reason is that the requirements are obviously tailored to the oil's base stocks (no thickening). The base oils of these all seasons are similar to many SAE40 formulations. It turns out a paradox - these oils become "record holders" without much effort - they obviously exceed the requirements of the standard by almost two times. In addition, it is difficult to normalize the general industrial minimum, which for some reason is growing all the time for no reason - for oils SAE80 and SAE100 according to J300, some atypical HTHS values would be required. That's just the logic here (appreciate!): And who said that the engine (!) Needs such viscosity values? For such oils, for this reason, there was simply nothing to even clearly motivate a special minimum requirement! The HTHS parameter for them remained at the level of more "liquid" oils - SAE40 ...
P.S
I wholeheartedly support "reclassifying" oils in any other way that is more informative(?) in relation to the engine than capillary leakage. That's just what happens (but did not happen, although it happened - HTHS flaunts something in the J300) with HTHS - this is just an imitation. Simulacrum. Yes, and admittedly unsuccessful.
To reinvent an informative quantity, it must be justified. The HTHS inventors, on the other hand, were in the business of fitting the abstract numbers to the numbers available for "pure" oils without thickeners. Moreover, roughly speaking, they divided the result in half, so that everyone could fit into the "standard".
Now, we still have the historically established SAE, but with the backing in the form of HTHS. A kind of pile, but with the inscription "do not drive below ground level." Navalny is not enough to check the financing of the 12-year (!) Labor of engineers from the SAE. Two-over-tsa-ti-years-no-go!
More or less, this parameter will play a role for highly thickened, easy-flowing bases, such as 0W40. But even there - at the level of measurement error. The strongest contrasts (with raw materials of the same quality) will hardly reach 10%. For example: Motul 300V 0W40 and 10W40 - 7% difference towards thicker 0W40 oil. Seven percent. With a tolerance in the SAE class - 30% or + -15%.
The vast majority of car owners who are engaged in the independent selection of lubricants for their car, at least have a general idea of such a concept as SAE classification.
The engine oil viscosity table, provided by the SAE J300 standard, subdivides all lubricants for engines and transmissions of automobiles, depending on the degree of fluidity at a certain temperature. Moreover, this division also determines the temperature framework for the use of a particular oil.
Today we will take a closer look at what the classification of lubricants is according to the table from the SAE J300 standard, and also analyze what meaning the values indicated in it carry.
What is a viscosity table
For ordinary motorists who are not engaged in a detailed study of the parameters of engine oils, the SAE oil viscosity table means the temperature range at which it is allowed to be filled into the power unit.
In a general sense, this is a correct statement. However, upon closer examination, it becomes clear that the data in the table do not quite correspond to the generally accepted opinion.
First, let's look at what the SAE oil viscosity table includes. It has a separation in two planes: vertical and horizontal. 
The classic version of the table is divided by a horizontal line into winter and summer lubricants (in the upper part of the table there are winter lubricants, in the lower part - summer and all-season lubricants). Vertically, there is a division into restrictions when using lubricants at temperatures above and below zero (the line itself passes through the 0 ° C mark).
On the Internet, and some printed sources, two different versions of this table are often found. For example, for an oil with a viscosity of 5W-30 in one of the versions of the graphic design of the SAE J300 standard, it is able to operate at temperatures from -35 to +35 ° C.
Other sources limit the scope of 5W-30 oil to the range from -30 to +40 ° C.
Why is this happening?
A completely logical conclusion suggests itself: there is an error in one of the sources. But if you delve into the study of the topic, you can come to an unexpected conclusion: both tables are correct, let's figure it out.
Detailed consideration of the parameters indicated in the table
The fact is that when the tables were designed and the algorithm for creating the dependence of oil viscosity on temperature was considered, the automotive technologies available at that time were taken into account.
That is, at the end of the 20th century, all engines were built using approximately the same technology. The temperature, contact load, pressure created by the oil pump, the scheme and design of the lines were approximately at the same technological level.
It was under the technology of that time that the first tables were created linking the viscosity of the oil and the temperature at which it can be operated. Although in fact the SAE standard in its pure form is not tied to the ambient temperature, but only stipulates the viscosity of the oil at a certain temperature.
The meaning of letters and numbers on the canister
The SAE classification includes two values: the number and the letter "W" - the winter viscosity coefficient, the number following the letter "W" - the summer one. And each of these indicators is complex, that is, it includes not one parameter, but several.
The winter coefficient (with the letter "W") includes the following parameters:
- viscosity when pumping lubricant along the lines with an oil pump;
- viscosity when cranking the crankshaft (for modern engines, this indicator is taken into account in the main and connecting rod journals, as well as in the camshaft journals).
What the numbers on the canister say - video
The summer coefficient (going with a hyphen after the letter "W") includes two main parameters, one secondary, and one derivative calculated from the previous parameters:
- kinematic viscosity at 100 °C (that is, at the average operating temperature in a heated internal combustion engine);
- dynamic viscosity at 150 °C (determined to represent the viscosity of the oil in the ring/cylinder friction pair, one of the key components in engine operation);
- kinematic viscosity at a temperature of 40 ° C (shows how the oil will behave at the time of the summer start-up of the engine, and is also used to study the rate of spontaneous flow of the oil film into the sump under the influence of time);
- viscosity index - indicates the property of the lubricant to remain stable when the operating temperature changes.
Often, several values are provided for the winter temperature limit. For example, for 5W-30 oil taken as an example, the permissible ambient temperature with guaranteed pumping of lubricant through the system should not be lower than -35 ° C. And for guaranteed cranking of the crankshaft by a starter - not lower than -30 ° C.
| SAE class | Viscosity low temperature | Viscosity high temperature | |||
| cranking | Pumpability | Viscosity, mm2/s at t=100°C | Min viscosity HTHS, mPa*s at t=150°С and speed shift 10**6 s**-1 |
||
| Max viscosity, mPa*s, at temperature, °C | Min | max | |||
| 0W | 6200 at -35 °С | 60000 at -40 °C | 3,8 | - | - |
| 5W | 6600 at -30 °С | 60000 at -35 °C | 3,8 | - | - |
| 10W | 7000 at -25 °С | 60000 at -30 °С | 4,1 | - | - |
| 15W | 7000 at -20 °C | 60000 at -25 °С | 5,6 | - | - |
| 20W | 9500 at -15 °C | 60000 at -20 °С | 5,6 | - | - |
| 25W | 13000 at -10 °C | 60000 at -15 °C | 9,2 | - | - |
| 20 | - | - | 5,6 | 2,6 | |
| 30 | - | - | 9,3 | 2,9 | |
| 40 | - | - | 12,5 | 3.5 (0W-40; 5W-40; 10W-40) | |
| 40 | - | - | 12,5 | 3.7 (15W-40; 20W-40; 25W-40) | |
| 50 | - | - | 16,3 | 3,7 | |
| 60 | - | - | 21,9 | 3,7 | |
This is where conflicting readings arise in the oil viscosity tables posted on different resources. The second significant reason for the different values in the viscosity tables is the change in engine production technology and the requirements for viscosity parameters. But more on that below.
Methods of determination and the attached physical meaning
Today, for automotive oils, several methods have been developed for determining all viscosity indicators provided for by the standard. All measurements are carried out on special devices - viscometers.
Depending on the investigated quantity, viscometers of various designs can be used. Let's consider several methods for determining viscosity and the practical meaning that lies in these values.
Viscosity when cranking
Lubrication in the necks of the crankshaft and camshaft, as well as in the swivel joint of the piston and connecting rod, thickens strongly with decreasing temperature. Thick oil has a large internal resistance to displacement of the layers relative to each other.
When you try to start the engine in winter, the starter noticeably strains. Grease resists crankshaft rotation and cannot form a so-called oil wedge in the main journals.
A rotary viscometer type CCS is used to simulate cranking conditions. The viscosity value obtained by measuring it for each parameter from the SAE table is limited and in practice means how much the oil is capable of providing cold cranking of the crankshaft at a particular ambient temperature.
Pumping viscosity
Measured in a rotational viscometer type MRV. The oil pump is able to start pumping lubricant into the system up to a certain thickening threshold. After this threshold, effective pumping of the lubricant and its pushing through the channels is difficult or completely paralyzed.
Here, the generally accepted maximum viscosity value is 60,000 mPa s. With this indicator, free pumping of lubricant through the system and its delivery through the channels to all rubbing nodes is guaranteed.
Kinematic viscosity
At a temperature of 100 °C, it determines the properties of the oil in many units, since this temperature is relevant for most friction pairs during stable engine operation.
For example, at 100 °C it affects the formation of an oil wedge, the lubricating and protective properties in friction pairs of the connecting rod pin / bearing, crankshaft journal / bearing, camshaft / beds and covers, etc.
Automated capillary viscometer and kinematic viscosity viscometer AKV-202
It is this parameter of kinematic viscosity at 100 °C that receives the most attention. Today, it is measured mainly by automated viscometers of various designs and using various techniques.
Kinematic viscosity at 40 °C. Determines the thickness of the oil at 40 °C (i.e. approximately at the time of summer start-up) and its ability to reliably protect engine parts. It is measured in the same way as the previous paragraph.
Dynamic viscosity at 150 °C
The main purpose of this parameter is to understand how the oil behaves in a ring/cylinder friction pair. In this node, under normal conditions, with a fully serviceable engine, approximately this temperature is maintained. It is measured on capillary viscometers of various designs.
That is, from the foregoing, it becomes obvious that the parameters in the SAE oil viscosity table are complex, and there is no unambiguous interpretation (including regarding the temperature limits of use). The boundaries indicated in the tables are conditional and depend on many factors.
Viscosity index
An important parameter that indicates the working qualities of the oil and determines its performance properties is the viscosity index. To determine this parameter, an oil viscosity index table and a formula are used.
Applied Formula for Viscosity Index
Shows with what dynamics the oil will thicken or thin as the temperature changes. The higher this coefficient, the less susceptible the considered lubricant to thermal changes.
That is, in simple words: the oil is more stable in all temperature ranges. It is believed that the higher this index, the better and better the lubricant.
All values presented in the table for calculating the viscosity index are obtained empirically. Without going into technical details, we can say this: there were two reference oils, the viscosity of which was determined under special conditions at 40 and 100 ° C.
Based on these data, coefficients were obtained that in themselves do not carry a semantic load, but are used only to calculate the viscosity index of the oil under study.
Conclusion
In conclusion, we can say that the SAE oil viscosity table and its linkage to permissible operating temperatures currently play a very conditional role.
It would be a relatively correct step to use the data taken from it to select oil for cars at least 10 years old. For new cars, this table is better not to use.
Today, for example, 0W-20 and even 0W-16 oil is poured into new Japanese cars. Based on the table, the use of these lubricants is permissible in the summer only up to +25 ° C (according to other sources that have undergone local correction - up to +35 ° C).
That is, logically, it turns out that Japanese-made cars can hardly drive in Japan itself, where in summer the temperature can reach +40 ° C. This, of course, is not true.
note
Now the relevance of the application of this table is declining. It can only be used for European cars over 10 years old. The choice of oil for a car should be based on the manufacturer's recommendations.
After all, only he knows exactly what gaps in the interfaces of the engine parts are selected, what design and power the oil pump is installed, and what capacity the oil lines are created.
An important indicator of 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, the extent to which the liquid lubricates the surfaces of the rubbing parts of the power unit depends on this characteristic. Its properties are influenced by external factors such as temperature, load and shear rate. That is why, next to the specific value, the test conditions are indicated.
What is the kinematic and dynamic viscosity of the oil?
In order to understand the difference, let's look at their characteristics.
The kinematic viscosity of an engine oil, which is measured in mm2 / s (cST), indicates its fluidity at normal and high temperatures. To measure this indicator, a glass viscometer is used. Note the time during which the lubricant flows down 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°C.
Dynamic viscosity is measured with a rotational viscometer that simulates conditions that are as close to real as possible.
The methods that determine the viscosity of an engine oil are pre-established in the SAE J300 APR97 specification. Following this particular certification, all lubricating fluids are divided into 3 types:
- summer;
- winter;
- all season.
If only numbers are used in the name, for example, SAE 30, SAE 50, etc., then these fluids refer to summer motor lubricants. If the number and letter W are used, for example, SAE 5W SAE 10W - winter lubricants. When 2 of these types are used in the class designation, such a liquid is called all-weather.
Let's take a look below at what SAE oil viscosities mean.
The SAE classification (Association of Automotive Engineers) separates all oils according to their ability to remain in a liquid state (flow), and lubricate well all parts of the power unit at different temperatures.
The above are temperature readings, depending on the value that determines the viscosity of the engine oil. The table shows at what temperature the fluidity of a particular fluid will not lose its lubricating properties.
Why is the viscosity of the oil important when changing the lubricant and what do the numbers mean?
A simple example to illustrate. As you know, the low viscosity of engine oil contributes to their normal operation in winter (SAE 0W, 5W). If the fluidity is low, accordingly, the oil film covering the parts of the power unit will be thin. The manufacturer in the technical manual indicates the permissible values, as well as tolerances for each type of engine. If you fill in a high fluidity grease, the motor will work with a load at an elevated temperature. This drastically reduces its motor resource.
And now vice versa. You are pouring liquid with fluidity below the indicated level. In this case, breaks in the lubricating film occur during operation, and the motor may jam. Oil viscosity as a function of temperature. No need to think that filling the engine with "super grease", which is used on sports cars, your car will start to "fly". It is necessary to fill in the fluid recommended by the manufacturer.
Another misconception is that some motorists do not distinguish the type of lubricants from their fluidity. So, for example, the viscosity of synthetic oils can be the same as mineral or semi-synthetic. In this case, they differ in composition, not physical properties.
What oil viscosity to choose for your car engine.
First of all, you need to look at the technical manual. The manufacturer indicates in the manual which oil viscosity is best suited for the engine in order to ensure its long-term operation. If it is not possible to see the recommended oil viscosity, then it is important to determine a few points:
- at what minimum and maximum temperatures your car will be operated;
- whether a load will be used (trailer, additional load or off-road driving);
- What is the condition of the engine (new or used).
Following these indicators, you must choose the viscosity of the car oil that will ideally lubricate the parts of the power unit.
A few words about other types of lubricants
transmission fluids
Transmission fluids meet SAE J306 classification. The viscosity of the gear oil depends on the operating temperature. As well as motor, transmission fluids are conventionally divided into:
- winter (SAE 70W, 75W, 80W, 85W);
- summer (SAE 80, 85, 90, 140, 250);
- combined (for example, SAE 75W-85).
To understand what kind of lubricant to use in the box of your car, you need to look at the recommendations and approvals of the gearbox manufacturer.
Hydraulic Lubricants
In addition to their primary function of transmitting pressure, hydraulic fluids also lubricate hydraulic pump parts. Based on this, they are divided into classes. The viscosity of hydraulic oil is low, medium and high. Below is a table showing the possible classes of hydraulic lubricating fluids.
