Generally, engine wear occurs during startup after the car has been stopped for driving for a certain period or in a cooling state. Lubricating oil slowly sinks from the transferring parts to the base when the engine stops operating. When the engine starts again, the only thing to partition the piston and cylinder is the chemical substances which are the remnants of lubricating oil adhered to the surface of the transferring parts. Before the lubricating oil circulates and forms a protecting shield at the surface of the parts, the only way to protect the engine is to add this chemical wet. In this transitional period, the friction at the surface may create serious engine wear and this condition will happen a few times a day after 15 minutes when the engine is initial startup.

The other reasons such as driving at great high speed, the car bearing a burden, such as dragging a car or car under a full load of people or things and traffic jams and going up a mountain (especially when the air conditioning is switched on) lead the engine to operate under a high temperature.