My boss just bought a 2009 Yukon Denali XL with the 6.2 liter motor. The dealer says whatever you do don't use BP gas that it is ruining the valves in a lot of Yukons they have seen. Has anyone here ever heard of such a thing? The mechanic says it is all over the internet. I can't find anything about it. Quite frankly I don't think the mechanic has the ability to test BP gas out to see if it really is ruining the valves.