Modern lubricants are made from refined oil. Oil manufacturers add special additives to them, which make up to 20% of motor oil. These additives, in particular, protect the oil from oxidation and prevent it from foaming at high speeds.
One of the indicators of viscosity-temperature characteristics is the viscosity index VI - this is an empirical, dimensionless indicator for assessing the dependence of oil viscosity on temperature. The higher the viscosity index value, the less the oil viscosity depends on temperature. Oil with a high viscosity index has better fluidity at low temperatures and higher viscosity at the engine operating temperature.
The life of engine oil is affected by factors such as the amount of water, fuel quality and the presence of combustion products. Therefore, regular oil changes are necessary.
Synthetic motor oil is more expensive than mineral oil in most cases. But the high price is compensated by reduced oil and fuel consumption and an increase in the oil change period.
Motor oil and its classification
(Material based on data from the portal: MercedesMan.ru)
Viscosity is the resistance to the flow of liquid. In winter, low-viscosity motor oils should be used to ensure easy engine starting. In summer, it is preferable to use more viscous oils.
SAE system (Society of Automotive Engineers of the United States). The oil designation indicates two viscosity grades: winter - with the letter "W" and summer - without a letter designation, for example SAE 5W-30. The lower the first number, the better the oil's fluidity at low temperatures. The higher the second number, the higher the oil's resistance to high temperatures.
ACEA System (Non-profit association of automotive engineers). The system has been in effect since 1996, replacing the CCMS system. Class A is used for gasoline engines, and class B for diesel engines.
SMSMS system (Union of Engineering Workers of the European Union). The oil designation consists of the letter "G" (gasoline engine) or "D" (diesel engine), as well as a single number. For example, CCMS G4. The higher the number, the better the quality of engine oil.
API System (American Petroleum Institut). The oil designation has two letters, the first of which is "S" (gasoline engine) or "C" (diesel engine). For example, API-SA or API-CA. The closer to the end of the alphabet the second letter is, the higher the quality of the oil.
Selecting engine oil
Mercedes accepts the standards of the European Union Machine Building Society (CCMC) and recommends the following oils for its petrol engines: CCMC-G4, CCMC-G5, API-SG, ACEA A2-96 or ACEA A3-96.
Oils classified by API or ACEA are used only if CCMC oils are not available.
In the European part with a wide range of summer and winter temperatures throughout the year, oil of viscosity grade 15 W-40 or 10 W-40 can be used. Only at very low or high temperatures persisting for a long time should oil of a different viscosity grade be used, consult a specialist for advice.