Enrique,

Enjoy your comments as always, however it is the "reputable sources" that has me concerned. How on earth could this conversation be considered "reputable" without any reference (or worse, discarded reference) to what was originally specified? Your octane rating and tire size examples reference original specification. Why not oil? Throughout this thread there is mention of temperature and operating conditions. What is the reader left with, though? Some vague idea that this might be important, perhaps, but nothing specific enough to warrant further thought? Perhaps the answer to this poor fellow's question is; "go ask a reputable source because you won't find it here"!

I've replied to Matt's post on the Z Club forum but thought you guy's might like this article from OZ.

http://www.animegame.com/cars/Oil%20Tests.pdf

Ps I've been running RP for years well before I read this article.

The '77 280z that my Mom gave me after my dad passed away has 400,000 miles on the engine and has had Amsoil 10W40 Synthetic in it since 27k miles :classic: