According to different filtering functions, it is divided into: oil filter, fuel filter (gasoline filter, diesel filter, oil-water separator, hydraulic filter), air filter, air-conditioning filter, etc. The engine has three kinds of filters: air, oil, and fuel, which are generally called "three filters", plus an air conditioner filter, commonly known as four filters. Responsible for the filtration of the lubrication system, the medium in the combustion system, the engine air intake system, and the cabin air circulation system.
