As long as your car engine is in a normal state, that is, without burning oil or leaking oil, the oil will not disappear out of thin air and can only circulate inside the password engine. Therefore, the oil in a normal engine will not be used up.

Although oil is inexhaustible, its function is lubrication.

Because of friction, there will be metal powder produced by metal wear and some carbon impurities produced by high temperature of the engine. These impurities are harmful to the engine and must be replaced.

In addition, the lubrication degree of engine oil decreases with the increase of time and mileage. Once the lubrication effect is not good, the engine will be damaged by friction.

This is also the main reason why the oil must be replaced, and this is also the reason why the oil must be replaced before it is used up.