Mobil 1 quietly changed their 15W50 to API SP?

[Slow Car Sport Mode]

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.

 

[userfriendly]

The 0w50 has a HT/HS of only 3.9 and VII of 202, which on paper seems nuts. Just seems like this is not designed to be a very shear stable racing oil.

Mobil 1 Racing™ 0W-50 Synthetic Oil | Mobil™ Motor Oils

Mobil 1 Racing™ 0W-50 is for racing engines. Its high-performance, full synthetic formula is specially balanced for friction reduction and optimum horsepower with outstanding wear protection.

www.mobil.com

Does a racing oil need to be shear stable?
The KV100C of an SAE 50 gives the engine the oil pressure it needs.
The somewhat low HTHS of 3.9 vs viscosity @ 100C provides more power, less heat generated from fluid friction and better fuel economy.

 

[Greasymechtech]

How long? How long does a 0w50 give you that oil pressure before it shears to a 40 or even a 30 grade? I'd wager that Mobil knows what they are doing but I don't expect their 0w50r to last too long as a 50. Some of us use the racing oils as 'snake oil additives'. A quart added to a typical 1-2 gallon sump can spike the visc and additive package without being excessive.

15w50 is a great top off oil for all those oil burners out there, regardless of whatever 16, 20, 30, or 40 grade that your engine was filled with during its quicklube/dealer/indie service. I don't own any engines that need a 50 grade anymore.

 

[FCD]

The 5W-50 has also been updated to SP.
And here in Europe up until now we still had the FS X1 version, now the X2 version has replaced it here too, took them 6 years to give us the X2 version!

 

[buster]

Does a racing oil need to be shear stable?
The KV100C of an SAE 50 gives the engine the oil pressure it needs.
The somewhat low HTHS of 3.9 vs viscosity @ 100C provides more power, less heat generated from fluid friction and better fuel economy.

Good point.

 

[userfriendly]

Good point.

Go to the "white papers and technical discussions" section and re-read "Viscosity improvers are not bad".
I learned a lot from that thread and bumped it up last year before it became lost in time.