Motor oil is essentially the lifeblood of any car. The role of engine oil is to keep the moving parts of the engine lubricated, to protect them against rust corrosion, and with modern detergent oil additives to keep them free of sludge and general engine gunk. The purpose of the Oil Filter is to keep the oil clean. Oil is pumped through the filter and then distributed throughout the engine. The filter traps debris and particles that would damage the engine.