Some soot particles are byproducts of fire which goes through piston circle and these blends into engine oil by leaking through crankshaft. Modern engine oils contain ingredients which hold soot particles of the suspension; thus, dirt buildup in the engine is prevented. Besides, as the soot particle buildup grows, the oil becomes stickier and loses its ability to lubricate. Furthermore, these soot particles are made of carbon so they are stiff and multiply abrasion significantly. To sum up, in order to minimize abrasion of the engine, soot particle buildup in engine oil must be as low as possible.
Full-flow filtering is not possible due to risk of filter getting choked and filtering (1 µm) small soot particles require an unpractical effort. Solution is to bypass filtering some of the engine oil at high standards. One of the most efficient processes of bypass filtering is cleaning of the oil by centrifuging.