I have read a article or two on the use of K&N filters in over the road commercial trucking. The trucking industry likes to run tests on engine oil to determine the condition of the engines. The trucks running the K&N filters have far more containments in the oil than the trucks running standard filters. If a K&N filter is not well oiled it will allow more dirt into the engine. Its a high maintenance item that can and will allow more fine dust into a engine if not cared for.