Why is it impossible, say, to make one oil for all cars so that the motorist does not suffer?
Alas, this does not work out, at least today, although the properties of motor oils have recently improved so much that it is almost impossible to make a gross mistake when choosing. And yet, the operating conditions of the oil in heat and cold are too different, in a gasoline engine and a diesel engine, and even with a supercharger. And everywhere, oil is required to reliably separate rubbing surfaces, preventing metal contact, wash out the smallest particles of wear and carbon formation, prevent corrosion, remove heat, wash off varnish deposits, not oxidize, not foam, not too thick in frost and not too thin at high temperatures., do not form precipitation and, finally, do not greatly change all these qualities over time. To do this, a whole range of additives is introduced into the oil: detergent, antifoam, depressant (so as not to thicken in the cold), antiwear, etc. Some additives combine several functions, for example, barium dialkyldithiophosphate is both an antiwear, anticorrosive and detergent additive.
In the USSR, GOST 17479.1-85 was in force and continues to be in force now, which determines the properties and marking of oils for piston automobile engines. Depending on the performance, six groups of oils have been established according to the degree of forcing and the type of engines for which these oils are intended.
Group A - for non-forced, B - low-forced, C - medium-forced and D - highly-forced engines. In addition, there is also group D - only for highly accelerated diesel engines and E - also for diesel engines, but stationary and marine, running on fuel with a high sulfur content. In addition, oils of groups B, C and D are further subdivided into carburetor oils with an index of 1 and diesel (index 2). The absence of an index indicates that the oil is suitable for both diesel and gasoline engines, but of course, this group according to the degree of forcing.
Another indicator underlying the domestic classification is the viscosity of the oil in centistokes (cSt) at an operating temperature taken as 100°C.
In order for the oil to easily start the engine in cold weather and at the same time retain its viscosity during operation, thickening additives - polyisobutylenes - are introduced into it. These are long molecular chains that tend to assemble into balls at low temperatures. In this state, they have almost no effect on the viscosity of the oil, it remains quite liquid. As the temperature rises, the coils of molecules "unwind" and thicken the oil, increasing its viscosity. This is how all-weather grades of oils are obtained, having an index in the designation "h".
So, here is an example of deciphering the domestic designation: M12G is motor oil having a viscosity of approximately 12 cSt at 100°C of group G, that is, for highly accelerated gasoline and diesel engines. Is it summer or winter? And in general, what are winter and summer when talking about oils? It is generally accepted that winter is when the average air temperature is mainly below 5°C, and summer is above 20°C. In addition, if the vehicle is operated in severe conditions (mountainous terrain, sandy and dirt roads), high viscosity oil should be used. M12G is a summer variety. In winter, it is preferable to use M8G oil. Although it must be said that most motorists have long preferred multigrade oils M53 / 1OG1 or M63 / 1OG1 to these brands. This marking means that this oil has a viscosity of 10 cSt at 100°C, and in frost it behaves like a winter oil with a viscosity of 5 or 6 cSt. Letter "h" - means thickened, not winter, as many believe. M53 / OG1 oil is more liquid, it is suitable for use in the middle lane and northern regions throughout the year. Oil U163 / 12G1 is more suitable for warm edges, as it is more viscous.
Our classification, for all its informativeness, is rather cumbersome, difficult to pronounce, and most importantly, it is not entirely clear what a low-, medium- and highly-forced engine is.
All over the world today, two types of designation of motor oils are accepted: according to performance properties (API) and viscosity (SAE).
The first type of classification was proposed by the American Petroleum Institute and looks like a combination of two letters: S (service) for petrol engines or C (commercial) for diesel engines with an additional letter indicating the degree of perfection of the oil. Moreover, this degree is expressed in a rather original way - through the years of production of engines for which this oil is intended. So, SA is an oil without additives for the oldest engines; SB - for newer engines; SC - for cars produced in 1964-67; SD - for engines 1968-72; SE - for cars manufactured since 1972; SF - since 1980. Of course, we are talking about foreign cars, modern Russian cars correspond to the SE, SF classes. The last two classes - SG and SH - are for the latest machines. As you can see, there are still a lot of letters in the Latin alphabet, so there will be no problems with labeling when the properties of oils improve.
Reference
Society of Automotive Engineers (SAE) proposed a classification according to viscosity at 100°C. It looks like this: SAE 20, SAE 40, etc. If the oil is winter, then its designation includes the letter "W". All-weather oils are designated according to the same principle as domestic ones, only through a dash, for example: SAE 20W-50. It should only be remembered that these numbers are not centistokes. For example, M63 / 14G1 oil corresponds to SAE 15W-40. The marking of all foreign oils contains, in addition to the name of the manufacturer, both types of designation, for example: Mobil SAE 10W-50 API SF. Sometimes the markings contain the words Super, Extra, Diesel, Turbo, Multigrade (all season) and so on.
Mineral, that is, derived from oil, motor oil has, as already noted, the following drawback - a strong dependence of viscosity on temperature. To reduce this phenomenon, thickening additives are introduced. But the trouble is, they quickly collapse due to high mechanical and thermal loads. This is especially noticeable on worn-out engines, where, after a run of several hundred kilometers in a new all-weather oil, the emergency red light suddenly lights up again. What to do? Switch to a thicker summer? But winter is in the yard, you won’t start the engine in the morning. The solution is to use synthetic oil.
They are obtained by chemical synthesis, which achieves high uniformity and stability of properties. But the most important thing is the viscosity "synthetics" changes little with temperature, that is, it is more liquid in the cold and thicker in the heat than "mineral water". This property will reduce the wear of parts and friction losses, which saves fuel - about 2-3%. Besides, "synthetics" burns less in the engine and generally lasts longer, forming few deposits. It is easy to distinguish synthetic oil by the inscription "synthetic", as well as over a wide temperature range: 5W-40, 10W-60, etc. The only bad thing is the high price, about 2.5-5 times more than mineral oil. Therefore, there is a compromise - semi-synthetic oils, that is, a mixture "synthetics" with mineral touch 50/50). It should be noted that you should not make such a mixture yourself, mineral oil additives may not dissolve in synthetic oil. As a result, "blood clots" in oil channels.
Reference
As for mixing two mineral or two synthetic oils, that's it. And do not believe the various instructions where it is forbidden to mix oils from different companies. Modern oil must undergo homologation, that is, approval for use, and one of the points of this procedure is a certificate of full compatibility. Indeed, can you imagine an American car owner who would have to constantly remember what kind of oil is filled in his car? When mixing various domestic oils, you can use the formula:
X = Ay + B (1 - y),
where X is the viscosity of the mixture, A and B are the viscosities of the oils being mixed, y is the proportion of the first oil in the mixture.
A few words about the choice of oil depending on the condition of the engine: During the break-in period, it intensively removes wear products from friction pairs and therefore it should not be thick. SAE 20, SAE 30 are best suited here, and from all-weather SAE 20W-30, 10W-30, 5W-30. During "maturity" for VAZ engines, SAE 30, 20W-30, 15W-30, 10W-40 are suitable. It is better not to use thicker ones yet because of the danger of oil starvation in the cold season. But the UZAM and MeMZ-968 engines need something thicker, since the first has larger gaps and worse oil scraper rings, while "Zaporozhets" high heat stress. Use SAE 20W-40, 10W-50, 10W-60 here. The same oils are suitable for any "elderly" motors.
Do I need to flush the engine when changing the oil? If the car has been running on high-quality oil all the time, then no, but at least once every two years or every 30,000 km it is still worth flushing the engine. Moreover, now there are compounds on sale that turn the filled old oil into flushing oil. It is not necessary, as before, to pour and fill several times, and the entire washing procedure will take you 5-15 minutes.