Engine oil serves three main purposes; most people probably already know oil lubricates the engine's internal components such as the bearings, crankshaft, camshafts and lifters. Perhaps less known are the remaining primary functions; cooling and cleaning. Oil cools internal engine components and keeps engine temperatures under control while detergents and additives remove carbon build up and dirt that has found its way into the crankcase through the combustion chamber by way of the air intake.
Today's engines run so cleanly that 10,000-mile oil change intervals are considered normal, but the job of the filter hasn't changed. It has to do its job well or the engine can suffer major damage.
It is highly recommended that the Oil Filter is replaced every time the engine oil is changed.