The main tasks of engine oil are lubrication and cooling of engine parts.
During normal operation, the engine consumes a certain amount of oil for the following reasons:
Engine oil is used to lubricate pistons, piston rings and cylinders (part of it enters the combustion chamber and burns). A thin layer of engine oil remains on the cylinder walls as the pistons move down. The vacuum generated during engine operation draws some oil into the combustion chamber. This oil, as well as oil from the cylinder walls, is burned during the combustion of the air-fuel mixture in the combustion chamber.
Oil consumption is strongly affected by the viscosity and quality of the oil, engine speed, driving conditions, etc. The engine consumes more oil under severe operating conditions, such as high speeds and frequent acceleration and deceleration.