I've read here a few times that Mobil 1 is the only full synthetic available over the counter. I've been using Esso (Canadian Exxon) Superflo synthetic for quite a few years (long before I knew there was a difference between the group III and IV syn's) anyways, its about a buck cheaper than Mobil ($5.48 per litre CDN) or about $3.30 USD per quart and according to the spec sheet and the tech line, it is still a full PAO/ester http://www.prod.esso.ca/pds/superflosynthetic.htm any comments ?? I've ran it 10,000-15,000 km in several vehicles and all have remained extremely clean and the one that I've torn down (1996 350 vortec) was in excellent shape with clean ring packs and visible crosshatching on cylinders with 190,000 km. Engine ingested water, not a lube problem.