I have about 80,000 miles on my 6.0 and with the winter weather the start-up sounds like a rod will poke out the side of the motor . I have used Mobile 1 5w-30 since day one . Anybody have any luck getting GM to replace the slappers ? My dealer says it will be fine. Anyone have their cylinders/rings cleaned through the spark plug holes quiet it down ? Or any other suggestions ?

 

Are you sure it is piston slap, and not lifter tick?