i've recently been researching this also. ln engineering have a good article on their site here:
Oils: What motor oil should I use? Which oil is best for my Porsche or aircooled engine?
where they suggest 5w40 is best. mobil 1 have two formulation that i can find; one for turbo diesels and one for mercedes. according to mobil the turbo diesel formula is also good for high performance gas engines, and has the SL/Cl-4 rating preferred by lne. researching that oil specifically i've found that lots of folks use it (or it's precursor delvac) and lne recommends it.
otherwise, i've read that the mobil 1 0w40 we get here is a different oil than what mobil sells in europe (different additive package).