I preferring running whatever is on sale. The kind of oil you run isn’t nearly as important as backing it with a quality filter and changing it regularly. But, I realize some of you are going to run the expensive stuff regardless.....in which case just stick with your Mobile 1. You should really check out this thread with regards to Royal Purple if you’re contemplating changing.....http://forums.stangnet.com/782089-ha-ha-royal-purple-busted-misleading-advertisements.html