Oil filter works can be divided into three types according to the general method of filtering impurities which are: mechanical separation, centrifugation and magnetic attraction.

Mechanical separation also can be further divided into three types according to their functions. It can be in the form of a purely mechanical separation, overhead separation and adsorption separation. Mesh filter is commonly found under purely mechanical separation category by using certain filter pore size to filter mechanical impurities and sludge. Filter impurities that larger than filter pore size are blocked and filtered out. Overhead separation refers to n small particles that adhere to the inner wall of the filter, and particles are gradually increased, and make the filter pore becomes smaller which cause formation of the overhead phenomenon that make the filtered particle have smaller size than the size of filter pore. Overhead phenomena easy to happen due to the irregular shape of oil particles. In addition there are gum substance in the oil often adhere to the filter surface or filter pore wall to form adsorption. Real situation of filtration not just involve single general principle of action, it may comprise of a combination of several actions.

Oil centrifuged by a high-speed rotation of the rotor, so that impurities in the oil thrown towards the inner wall of the rotor by centrifugal force, so that separated from the oil.

Is the use of a permanent magnet magnetic attraction force of the magnetic iron particles adsorb the oil, let them cycle back and forth in the oil lubrication system, harm engine parts

Magnetic attraction use permanent magnetic magnet to adsorb iron particles in the oil to stop them to cycle back in the oil lubrication system which can cause harmful to engine.