If you go to the Amsoil website and click on "What's New", there is an interesting brochure, "G-1971" that compares a bunch of synthetic and petroleum oils using standard API test methods....It includes new test data for both "ATM" and the 10w-30, Supersyn, along with Valvoline Synpower, Castrol Syntec and the Pennzoil/QS synthetics ....
Interestingly enough, some of the Group III based oils perform extremely well, which is no surprise to me....