Remember that in NASCAR's top three series, 129 cars/trucks start each week (43+43+36) and of those, probably half the cup cars, maybe quarter of the Nationwide cars and maybe five or six trucks have an oil affiliation. I wouldn't be the least bit surprised if the vast majority of those that don't have a deal do use Mobil One. It has a good reputation, is availible everywhere, is fairly cheap, and since they are a NASCAR contingency sponsor, there's a lot of freebies floating around. I would say it it was probably the top oil in ARCA (same engines as Cup, except roller cams allowed) while I was there, and unless you were running an R&D engine program for a Cup team, it was straight off the shelf. We used 76 Racing Oil and Mobil One right off the shelf and had zero oil related engine issues. There is a BIG difference between what the Hendricks, Gibbs, Roushes, annd Childresses do and what EVERYBODY ELSE does.