Fuel filters are divided into three categories: diesel filters, gasoline filters, and natural gas filters, which act on filtering impurities in the engine fuel system.
The function of the fuel filter
A fuel filter is used to filter the fuel (gasoline, diesel) used for engine combustion, preventing harmful particles and water such as dust and metal powder from entering the engine, protecting the moving parts such as the oil pump nozzle, cylinder liner, and piston ring, reducing mechanical wear and avoiding blockage.
Diesel filter 
Diesel fuel that has been precipitated or filtered can cause diesel pollution during the refueling process due to factors such as refueling tools and environment. In addition, during the operation of diesel engines, impurities and air dust deposited in the fuel system can also cause diesel pollution. Therefore, diesel filters for vehicles are essential.
The structure of diesel filters is roughly the same as that of oil filters, divided into two types: replaceable filters and rotary filters. The working pressure and oil temperature resistance requirements of diesel filters are much lower than those of oil filters. But the requirements for the filtration efficiency of diesel filters are much higher than those of oil filters. The diesel filter element is mostly made of filter paper, and some also use felt and polymer materials.
Gasoline filter
The main function of a gasoline filter is to filter out impurities in gasoline.
Gasoline filters are divided into carburetor type filters and electronic fuel injection type filters. For gasoline engines that use carburetors, the gasoline filter is located on the inlet side of the fuel pump, with a relatively low working pressure, and generally uses a nylon casing. The gasoline filter of an electronic fuel injection engine is located on the outlet side of the fuel pump, with a high working pressure and usually uses a metal casing.
If the gasoline filter is too dirty or blocked, the power will start slowly at the fuel door, making it difficult to start the car and requiring multiple ignition. Most engines use disposable, non removable, paper filter gasoline filters with a replacement cycle of generally 10000 kilometers. The filter has an oil outlet arrow mark, do not install the filter upside down when replacing.