FWIW - I have always run 1 - 1.25 quart of 80-90 synthetic Lucas or Valvoline. If the rear end if completely dry - I use 1.5 qt. There was a thread on here a while back - and the opinions and experiences varied. The only other thing, I remember reading on the MW site years ago that they didn't favour synthetic. When I used dinosaur oil, I had no different experience, except cold mornings.
