Best oil weight/viscosity for a bone stock car's first track day?

[Spart]

BTW, per Savage Geese and Limit+1 & Engineering Explained, 0W30 will be thinner at high temps than 5W30 because the friction modifiers needed to get to 0W will sheer at higher temps. Just food for thought.

I think you mean Viscosity Index Improvers (VIIs) not friction modifiers.

But yes the point stands, 0W-anything will have a hard time holding up to a good 5W-30.

I run 0W-40 primarily because where I live, temps can and do get down to the -30°F range before the wind chill. The worst thing you can say about a 0W-40 is that it will sheer down to a very thick 0W-30 after a few thousand miles. Not a bad thing if you're aware of it and the situation is right!

If I lived somewhere a bit warmer, I would run a 5W-30 or 5W-40. There are some pretty good 5W-40 oils out there that give you some nice high temp performance without sacrificing all that much cold start protection.

When I had a Shelby GT350, it called for 5W-50 oil. That oil would sheer down to the very top of the 40 range based on the used oil analysis reports, but it also never felt like the engine was having a hard time turning over when I would start it every three weeks or so throughout the winter. Essentially the same engine in the Mustang GT called for 5W-20, but the GT350 came with a gas guzzler tax and the GT did not. Food for thought!

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[shijima_ending]

I think you mean Viscosity Index Improvers (VIIs) not friction modifiers.

But yes the point stands, 0W-anything will have a hard time holding up to a good 5W-30.

I run 0W-40 primarily because where I live, temps can and do get down to the -30°F range before the wind chill. The worst thing you can say about a 0W-40 is that it will sheer down to a very thick 0W-30 after a few thousand miles. Not a bad thing if you're aware of it and the situation is right!

If I lived somewhere a bit warmer, I would run a 5W-30 or 5W-40. There are some pretty good 5W-40 oils out there that give you some nice high temp performance without sacrificing all that much cold start protection.

When I had a Shelby GT350, it called for 5W-50 oil. That oil would sheer down to the very top of the 40 range based on the used oil analysis reports, but it also never felt like the engine was having a hard time turning over when I would start it every three weeks or so throughout the winter. Essentially the same engine in the Mustang GT called for 5W-20, but the GT350 came with a gas guzzler tax and the GT did not. Food for thought!

With that said, does anybody know at what temps the cold start protection would actually matter on a 0w vs. a 5w? For example I live in southern California. I’m wondering if it ever even gets cold enough to where a 5w is a little too thick for the engine’s liking upon startup.

 

[Spart]

With that said, does anybody know at what temps the cold start protection would actually matter on a 0w vs. a 5w? For example I live in southern California. I’m wondering if it ever even gets cold enough to where a 5w is a little too thick for the engine’s liking upon startup.

I would run a 5W where you are at without hesitation, especially since (as noted earlier in the thread) the UK owner's manual specifies 5W-30.

Just make sure to look for an API SN or SP spec and then whatever flavor of the rainbow you like best.

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