Mobil 1 quietly changed their 15W50 to API SP?

Nov 29, 2021
Buster remember though in Nascar they run like 20+ quarts of oil in their oil system... So it has plenty of time to cool within the lines away from the motor and in the oil tank too. That and the oil is on the motor for quite short period of time which helps also. And I bet if they run a 0w40 or even 0w30 they have that factored in and if it were to shear down one grade they would be ok with that.

I'd bet those other cars racing like IRL and GT etc etc may have a similar set-up running in them too.

I hope you and your family are doing good man.

Always good to see you on here.
They also use a 36psi or greater cooling system pressure/cap, since most engine cooling in a water-cooled application is from this aspect of the engine. Yes, oil cools, but there is argument that its main function is to transfer heat from moving parts, as well as lubricate, and plenty of research indicates that thin oil achieves this better, point of this post was as to Nascar and large oil capacity. Cars like Mercedes-Benz and others have had large 9/10 quart oil capacity (other engines have higher capacity. I think Bugatti Veyron W16 has 16 quart sump) - NASCAR, Mercedes Benz, Bugatti Veyron, all I'm saying is that in Nascar you have 36psi+ cooling system
and on a Chevy Cruze it is 20psi cooling system, above your usual 16 or oddball 15 (90s GM) psi spec . And that helps the engine out in that extreme application.