Do you have any info on how GM tested Mobil 1 in the Corvette?

[Jimmy_Russells]

Which was true, in Europe (at the time), as they had low sulphur gas. But the OE drain intervals weren't doable with that oil on this side of the pond with the gasoline we had available.

And to make it even more confusing that was ESP Formula, which was made in France, whereas the newer stuff is just 'ESP' and made in Texas.