You know, there are so many claims about oils, it is very hard to sort the signal from the noise. I have never had a oil related failure in any engine, even when I ran 2 cycle Moto-X bikes. I can say that the main and rod bearings in my GT-1 cars' motor (ex Tony Stewart's Gibbs Racing motor) that is being rebuilt as we speak, look very good after 3 years of Royal Purple #21 racing oil. Having said that, I always used Mobil 1 in all of my street cars and ran my tow vehicle for over 150K miles and still did not burn any oil. Brad uses Amsoil with good success as well and I think most of the good brands of motor oil that meet the GM Standard 4718M will be good. Where a difference can really be found is in the MN6 trans. In our '01 ZO6 T1 car, we found that the Mobil Synthetic ATF really did not work very well when the temps got hot, but the Royal Purple "Syncromax", and the RedLine MTL did. Brad, does Amsoil make a manual trans lube?
Have you used it?
BTW, what do you use in a submarine gearbox? I saw on the side of an USAF KC-10 jet engine, "Service with Mobil 2 jet only". I know they are an apples and oranges comparison, but interesting nonetheless.