There are three types of fuel filters: diesel filters, gasoline filters and natural gas filters. Its function is to filter out harmful particles and water in the engine fuel gas system to protect the oil pump nozzle, cylinder liner, piston ring, etc., reduce wear and avoid blockage: 

1. The structure of the diesel filter is roughly the same as that of the oil filter. There are two types: replaceable and spin-on. But its working pressure and oil temperature resistance requirements are much lower than those of oil filters, and its filtering efficiency requirements are much higher than those of oil filters. The filter element of the diesel filter is mostly filter paper, and some are made of felt or polymer materials.
2. Diesel filter can be divided into diesel water separator and diesel fine filter. The important function of the oil-water separator is to separate the water in the diesel. The presence of water is extremely harmful to the diesel engine fuel supply system, rust, wear, and seizure can even worsen the combustion process of diesel. Due to the high sulfur content in Chinese diesel, when combustion occurs, it will even react with water to form sulfuric acid to corrode engine parts. The traditional way of removing water is mainly precipitation, through the funnel structure. Engines with emissions from National III and above put forward higher requirements for water separation, and the high requirements require the use of high-performance filter media.
3. Gasoline filter is divided into carburetor type and electronic injection type. For gasoline engines using carburetor, the gasoline filter is located on the inlet side of the fuel transfer pump, and the working pressure is relatively small. Generally, nylon shells are used. The gasoline filter of an EFI engine is located on the outlet side of the fuel transfer pump, and the working pressure is relatively high, and a metal casing is usually used. The filter element of the gasoline filter mostly uses filter paper, but also uses nylon cloth and polymer materials.
4. Gasoline filter because the combustion method of gasoline engine is different from that of diesel engine, the overall requirements are not as harsh as diesel filter, so the price is cheap.