During the quality assurance period of the new car, a substitute for the filter (filter element) should not be used. Even if the quality assurance period has passed, the filter should be selected carefully. The performance of diesel filters is graded according to ISO standards. In addition to the performance test according to the SAE standard, the air filter element must also undergo a bench test to meet the requirements of the original intake resistance of the rated intake air volume of the engine. A qualified oil filter must conform to the original designed engine cylinder pressure, oil temperature, flow rate, viscosity and vehicle use conditions, etc., and must consider the comprehensive balance of core quality. The hydraulic oil filter element is marked on the manufacturer’s product sample or nameplate with the nominal filtration accuracy, not the absolute filtration accuracy. Only the β value measured through the test can represent the filtration capacity of the filter. The hydraulic oil filter element should also meet the requirements of pressure loss (the total pressure difference of the high pressure filter is less than 0.1PMa, and the total pressure difference of the oil return filter is less than 0.05MPa) to ensure the optimization of flow and filter element life.