The diesel filter element should be replaced every 40,000 kilometers. If it is not replaced for a long time, it will affect the power, because the function of the filter element is to filter impurities and moisture. According to the quality of gasoline, it is best to replace the car after running for about 30 thousand kilometers, but if it is genuine, it will damage the oil pump and injector if it is not replaced for a long time. Oil-water separator is a kind of machinery, which is usually used for restaurant sewage treatment. Due to the requirements of environmental protection, the sewage discharged to the ship machinery places in rivers, lakes and seas must be treated and an oil-water separator is needed. It is recommended to change the diesel filter twice and the wooden filter once. The oil-water separator should be drained frequently and replaced once every six months, depending on the situation: 1. Oil-water separator is a separator that uses gravity sedimentation principle to remove impurities and moisture according to the density difference between water and fuel, and has separation elements such as diffusion cone and filter screen inside; 2. The oil-water separator has other functions, such as preheating fuel to prevent wax deposition and filtering impurities; 3. It is a kind of fuel filter, and its main function is to remove water from diesel oil, thus reducing the faults of fuel injectors and prolonging the service life of engines; 4. Oil-water separator can only separate oil and water in engine oil, which has a certain effect on improving engine oil combustion. It is recommended to replace it every 20,000 kilometers, together with the oil-water separator. If it is not replaced for a long time, it is easy to damage the nozzle and pump. If there is water and impurities in diesel oil, the parts of fuel system will be corroded and rusted by the water in diesel oil. Removing water from diesel oil is very important for trouble-free operation and prolonging service life of fuel system. The oil-water separator plays this role.