The function of the oil filter:

Its function is to filter out harmful particles and water in the engine fuel gas system to protect the oil pump nozzle, piston ring, cylinder liner, etc., reduce wear, and avoid clogging. Remove the iron oxide, dust and other solid impurities contained in the fuel to prevent the fuel system from clogging (especially the fuel injection nozzle). Reduce mechanical wear, ensure stable engine operation, and improve reliability.

Even though the diesel is cleaned by sedimentation and filtration before being added to the diesel engine fuel tank, in the refueling process, due to factors such as refueling tools, refueling environment, and unclean fuel tank ports, it will still be polluted. The impurities deposited in the fuel system and the suspended particles in the air will also pollute the diesel. Therefore, the diesel filter on the car is essential, not to mention that the diesel is not necessarily really clean before being added to the fuel tank.