The lifters on my car make a loud tapping sound almost all the time, and I don't know how much more of it I can take. I have tried Slick 50, Marvin's Mystery Oil, and almost every different motor oil there is. Nothing works for more than a few days. Replacing the lifters will cost me almost $2K, so that is definitely not an option. Can you all share some of your success stories of quieting those noisy lifters? Many thanks.