Modern motor oils, consisting of base oils and a selected set of additives, are divided into two main types:
- mineral (obtained by distillation from petroleum) - their viscosity is highly dependent on temperature. To stabilize the properties, various additives are used, which, in turn, are destroyed quite quickly due to high mechanical and thermal loads, reducing the service life of the oil;
- synthetic (obtained by chemical synthesis) - have high homogeneity and stability of properties. They remain more liquid in the cold and thicker in the heat, burn less in the engine, form fewer deposits, and have a longer service life.
Note. Synthetic oils do not destroy engine seals, but when using them, leaks may occur through worn seals due to the greater fluidity of synthetic oils compared to mineral oils. The service life of synthetic oils is only slightly longer than that of mineral oils. Rapid darkening of the oil only indicates its good cleaning properties and a contaminated lubrication system.
The intermediate position is occupied by the so-called semi-synthetic oils. They are made on a mineral basis, but with additives of synthetic components, therefore, their quality is close to synthetic oils, but they are much cheaper.
One of the main properties of motor oil is its viscosity, which determines the temperature range of motor oil application. At low ambient temperatures, motor oil must have low viscosity to ensure engine start-up and supply of motor oil to its components. At high temperatures, motor oil must be more viscous to maintain the required oil pressure in the lubrication system. According to viscosity, motor oils are divided into three types:
- winter - due to low viscosity, they ensure engine starting and lubrication of the main components at negative ambient temperatures;
- summer - due to high viscosity, they provide lubrication of engine parts at high ambient temperatures;
- all-season - at low ambient temperatures they have the viscosity of winter oils, and at high temperatures they have the viscosity of summer oils.
Attention! It is strictly forbidden to use motor oils:
- - not intended for gasoline car engines;
- - with inappropriate performance characteristics;
- - not corresponding to the season in viscosity (according to SAE classifications).
[This note was copied from the resource: renaultbook.ru]