Gasoline filters usually have only one stage, installed between the gasoline tank and the gasoline pump or between the gasoline pump and the carburetor. Since there are three precision parts in the diesel engine supply system, the cleanliness of diesel is required to be high, and the colloid content in diesel is high. In order to improve the filtering efficiency, diesel filters usually have two or more stages, which are divided into diesel coarse and fine filters, also known as oil-water separators and diesel fine filters. They are installed between the diesel tank and the fuel pump, and between the fuel pump and the injection pump. Some diesel engines are also equipped with a sedimentation cup to precipitate water and impurities in the diesel.