Here's my (not too serious) thesis: Castrol Group III, for all intents and purposes, was just as good as Mobil 1. It's just a matter of breaking apart larger molecules v. putting together smaller ones. The real superiority of Mobil was in their marketing department, not their chemistry. Not only their synthetic product but their dino. products have now been tarnished forever by the fact that they cheated. In reality both Castrol and Mobil are roughly equal. Only the PR guys are demonstrably superior at Mobil! Have at me!