We were sitting around the shop one afternoon and got onto the subject of how Pennzoil is cheaper than most, and compared to most other leading brands of conv. oil, causes sludge. Now this did not make a lot of sense to me because my thought was that the API rating of SM on the Pennz's bottle should mean that the oil will protect from sludge. I did not speak up because I did not know for sure the facts of Pennzoil but I hope we can fix that.