Originally Posted By: Patman
This is what makes me confident in my choice of using M1 ESP Formula 5w30 in place of M1 ESP Formula 0w40 (which is now factory fill on the Corvettes, and recommended by GM for use in the 2014-2018s too) The 0w40 might have a higher viscosity at 100c (12.9 vs 12.1) but the 5w30 actually has a slightly better HTHS (3.58 vs 3.53) I know it's not a huge difference, but I'm happy that it's even close to the same HTHS, while most likely being the more shear stable of the two choices. And either of these two choices is a step up from the regular M1 5w30, which has an HTHS of only 3.1, which I think is just a tad low for those times when I want to have some fun and make a few full throttle blasts.
I think it's a good call, and would be the one that I'd make personally.
Originally Posted By: Virtus_Probi
I'd actually argue that an oil with a relatively low 100C viscosity and a relatively high HTHS (compared to competitors of the same grade) would give a great combination of wear protection at critical spots in the engine as well as lower general frictional losses (=better gas mileage).
Too bad many of the big makers don't share HTHS for all their oils...
Pick your HTHS point, and choose the oil with the Harman Index closest to "1", it is closer to a Newtonian.
5W30 Dexos 2 could be the staple for almost everyone (who doesn't need 0W of course).
If they had Dexos 2 10W30, I'd buy it.
Originally Posted By: ka9mnx
More great info. Thanks Shannow! I'm still digesting them. Hard to see the fine print with my old eyes.
You have me thinking, in my climate, I could get by (additives permitting) with a straight weight. But I was thinking 30w? Probably won't because I'm happy with the HTHS of the oils I use. May try the 10w-30 in the Ranger next time...
No problems
Google
The relationship between Engine Oil Viscosity and Engine Performance, Part 2
It's where I got a lot of my stuff, if you can find a preview in Google Books, you can blow it up and see some of the context.