There are two types of oil filters installed before and after the oil pump. The one installed in front of the oil pump is called the oil strainer. According to the arrangement mode, the oil pump installed behind the oil pump can be divided into full flow type and split flow type. The function of the oil filter is to filter out the metal wear debris, mechanical impurities and oil oxides in the oil. If these impurities enter the lubricating system with the oil, they will aggravate the wear of engine parts, and may also block the oil pipe or oil passage.

Classification of oil filters: full flow type and split flow type.

The oil filter is one of the four filters. The other three filters are air filter, air conditioner filter and fuel filter. The role of the oil filter is to filter impurities in the oil and protect the engine from wear.

Full flow oil filter: Most of the full flow oil filters used in modern automobile engines are filter type. The oil enters the filter center from the periphery of the paper filter element, and then flows into the main oil passage of the engine body through the oil outlet. When the oil flows through the filter element, impurities are trapped on the filter element. Split flow oil fine filter: There are two types of split flow oil fine filter: filter type and centrifugal type. The filtering type has the contradiction between filtering capacity and passing capacity, while the centrifugal type has the advantages of high filtering capacity, large passing capacity, and not affected by sediment. Therefore, the centrifugal oil filter is often used as the split flow fine oil filter in vehicle engines.

The filtering principle of oil filter can be divided into three categories: mechanical separation, centrifugal separation and magnetic adsorption.

1. The common mechanical separation is grid filtration. There are holes of certain size on the surface of the filter material. The solid particles in the engine oil, which are larger than the holes, are blocked on the outer surface of the filter material,
2. Centrifugal separation is to make the oil pass through a high-speed rotating rotor, and the impurities in it are thrown to the inner wall of the rotor under the centrifugal force, so as to separate from the oil.
3. Magnetic adsorption is to use permanent magnets to absorb iron particles in the engine oil to prevent them from circulating back and forth in the engine oil and harming the machine parts.