How many types of air filters are there on a car?

Air filters can be classified into several types, including filtering type, centrifugal type, oil bath type and combined type. At present, the commonly used air filters in engines mainly include inertial oil bath air filters, paper dry air filters, and polyurethane filter element air filters, among others. The inertial oil bath air filter undergoes three levels of filtration in sequence: inertial filtration, oil bath filtration, and filter filtration. The latter two types of air filters mainly undergo filtration through filter elements. Inertial oil bath air filters have the advantages of low intake resistance, adaptability to dusty and sandy working environments, and long service life. They were previously used in the engines of various types of automobiles and tractors. However, this type of air filter has a low filtration efficiency, is heavy, costly and inconvenient to maintain, and has gradually been phased out in automotive engines. The filter element of the paper dry air filter is made of microporous filter paper treated with resin. The filter paper is porous, loose and folded, with certain mechanical strength and water resistance. It has the advantages of high filtration efficiency, simple structure, light weight, low cost and easy maintenance. It is currently the most widely used air filter for automobiles. The filter element of the polyurethane filter element air filter is made of soft, porous and sponge-like polyurethane, which has strong adsorption capacity. This type of air filter has the advantages of the paper dry air filter, but its mechanical strength is low. It is widely used in car engines. The disadvantages of the latter two types of air filters are their relatively short service life and unreliable operation under harsh environmental conditions.