I'm on the other side of the coin on Pennzoil that the two previous posters. It is the only oil that has been run in my '77 Ironhead, '85 Chevy powered boat, '90 5.0 Mustang, and '89 Jeep (since 60k miles), and '94 Toyota pickup. They are all doing just fine on it. I elected to have a timing chain put in the Toyota at 100k because they were prone to break. The mechanic that did it commented on how extremely clean the inside of the engine was.