What causes oil stains on the engine cover?

[WillowRose]

It's normal. The car has been used for too long, and the engine oil seal has aged, unable to retain the oil. Concept: An engine (Engine) is a machine capable of converting other forms of energy into mechanical energy, including internal combustion engines (reciprocating piston engines), external combustion engines (such as Stirling engines, steam engines, etc.), jet engines, electric motors, etc. For example, an internal combustion engine typically converts chemical energy into mechanical energy. Classification: Internal combustion engines, external combustion engines. External combustion engines refer to those where the fuel burns outside the engine, such as gas turbines and jet engines.