True story,a guy I know is super cheap, he stopped by one time to let me listen to a knock in his 80's Ford PU with a 300 6 cylinder.I heard the main bearings pounding when he pulled up.I told him he needed a new engine or at least an expensive repair job.He was not happy, said the truck engine should last longer than 130,000 miles.I pulled the oil filler cap,the inside of the valve cover was solid goo, the PCV was plugged, the engine was misfiring badly besides knocking.I asked him when he changed the oil . His answer was he only changed the oil 3 times in 130k miles.I closed the hood.
