I was in WM today back by the oil section and ran into a guy pulling a 5 qt. jug of M1 5-30 off the shelf. We started talking oil and M1 use, and he told me his 02 Dodge truck(5.something) had lifter clatter for some time. His Chrysler mechanic told him his engine had some sludge build up and was causing the clatter. The mechanic told him their cure for that problem was start using synthetic oil, so he did. This was three years ago and the lifters are quite now after several OCIs with the M1. I thought this was interesting, and shows the cleaning ability of synt. oil.