[Katech_Zach]

I used Valvoline VR1 Racing 20w-50 in my 8000 RPM LT4 for track use.

For street/track guys, i would use the new Z06 oil Mobil1 Supercar 5w-50

[Canyonero]

Originally Posted by wakespeak

With 15w-50 I see regular 275F-280F temps on GM recommends the higher viscosity oil for cornering protection, then only for the ZL1 1LE.

Presumably this is because a ZLE comes with Supercar 3Rs. An SS or ZL1 can achieve the same Gs on R Compounds.

Does this mean everyone on sticky tires should be switching to thicker oil on track?

Other than emissions/mileage, is anything harmed by leaving in thicker oil all the time and letting the car warm?

[Msquared]

15w50 is not recommended because oil pickup issues. It's recommended because it's high-temp/high-shear viscosity is a lot higher than that for 0w40. That's the main metric that matters in a track situation. The HTHS for 0w40 Supercar is 3.53, but for 15w50 it is 4.5. They don't publish that spec for the 5w50 Supercar stuff, which is maddening. Going from memory, the ESP 0w40 x3 (i.e. not the Supercar, but still Dexos 2) is about 3.8.

The operating temps between all these grades shouldn't be that much different, because they all thin out a lot at full temps: the 100C kinematic viscosity for 0w40 is 12.9 vs 18 for both w50 oils. That's thin in comparison to the 40C viscosities, which range from 69 - 125. And that is the main reason you don't want to daily drive the 15w50: even on a very hot summer day, a cold start gives you almost twice the resistance to flow as the 0w40. The other thing is that the Dexos 2 oils are specifically made to minimize fouling the cats and building up deposits on intake valves. The latter is a common issue for DI engines. Again, if you have a ZLE and just drive it to track events, that isn't a big deal, but I wouldn't daily drive on oil that isn't Dexos 2 certified.

[Canyonero]

Is a mostly tracked regular ZL1 / SS not better off with thicker oil for cornering?

I have been using 5W-40 Motul (Dexos 2) but reading that GM recommends 15w-50 because of cornering forces makes me wonder if we should be going thicker.

[Msquared]

Originally Posted by Canyonero

Is a mostly tracked regular ZL1 / SS not better off with thicker oil for cornering?

I have been using 5W-40 Motul (Dexos 2) but reading that GM recommends 15w-50 because of cornering forces makes me wonder if we should be going thicker.

Again, whoever started that trope about thicker oil being better for cornering should be forced to drink motor oil. That's just not at all what matters. At 100C, 15w50 has a viscosity of 18 and 0w40 is around 12. They are both going to move the same amount in the pan due to cornering force, it's just that the 15w50 is going to take a few milliseconds longer to move. It's irrelevant.

If you're relying on thick oil to prevent your pickup from being uncovered during cornering, you might as well start saving now for a new engine. OTOH, GM thoughtfully gave us 10qt pans that don't ever let the pickup run dry if the sump is properly filled before going out on track. Plenty of people autocross these cars on tires far stickier than either Goodyear that comes on either V8 1LE. The pickup never starves for oil. We need to stop with this shit.

[Canyonero]

Originally Posted by Msquared

Again, whoever started that trope about thicker oil being better for cornering should be forced to drink motor oil. That's just not at all what matters. At 100C, 15w50 has a viscosity of 18 and 0w40 is around 12. They are both going to move the same amount in the pan due to cornering force, it's just that the 15w50 is going to take a few milliseconds longer to move. It's irrelevant.

If you're relying on thick oil to prevent your pickup from being uncovered during cornering, you might as well start saving now for a new engine. OTOH, GM thoughtfully gave us 10qt pans that don't ever let the pickup run dry if the sump is properly filled before going out on track. Plenty of people autocross these cars on tires far stickier than either Goodyear that comes on either V8 1LE. The pickup never starves for oil. We need to stop with this shit.

Ok, this makes sense now. Thank you for explaining!

[wakespeak]

Originally Posted by Canyonero

Presumably this is because a ZLE comes with Supercar 3Rs. An SS or ZL1 can achieve the same Gs on R Compounds.

Does this mean everyone on sticky tires should be switching to thicker oil on track?

Other than emissions/mileage, is anything harmed by leaving in thicker oil all the time and letting the car warm?

I think its because the ZLE is expected to be more likely exposed to regular track conditions. The extra viscosity I always assumed it helped compensate for the lack of dry sump lubrication, lingering longer on parts in high G/high temp conditions. M1 15w-50 also has high anti-wear additives that kick in if the oil film thins out. I doubt the reason for 15w-50 is to keep the oil pickup covered.

In oil tests by other LT4 owners 15w-50 was fine in mixed street/track use. If you live in a colder climate and/or don't give the engine at least 30s after startup to move the oil, then switch back to 0w-40. The higher additives in 15w-50 could shorten your catalytic converter life some - a concern if you live in a strict emissions testing area and plan on holding the car for a while.

[JSH]

I've owned the car for three years and used either 5W30 or 0W40. Put Mobil 1 Supercar Full Synthetic Motor Oil, 0W-40, Dexos R in it last week.

[zapp]

Is anyone running the Mobil1 Supercar 5w50 for street and track duty?
Got this from ChatGPT: "The High-Temperature High-Shear (HTHS) viscosity of Mobil 1 Supercar 5W-50 is approximately 4.4 mPa·s at 150°C, as reported for the Mobil 1 FS X2 5W-50 variant. "

I just switched from the Motul 5w40 to the Mobil1 Supercar 5w50 and I'm wondering if a track day would really require another oil change to e.g. the Motul 300V 15w50?

[Msquared]

Not a ZLE, but I just began running Supercar 5w-50 as my all-purpose oil in my SS 1LE. I made this change when the car stopped being my daily driver. I use it for autocross and track days, and it still gets driven to/from events and the occasional other duties as assigned.

FS X2 and Supercar 5w-50 are definitely not the same oils, so you can't apply the specs from one to the other. And Mobil frustratingly doesn't publish an HTHS number for the Supercar variety. However, Supercar actually has a slightly higher 100C viscosity and a fair amount of zinc, so my guess is that its HTHS is slightly higher than that for the FS X2 (which Mobil specs as 4.3).

I don't know enough about the Motul products to say if you need to switch, but my guess is that it would still be a good idea.

[USMUCL]

I'm reading more and more SLE folks change from 0w40 to the 5w50 supercar, especially for track dedicated use.

Mine is track dedicated, but I couldn't bring myself to commit . . . so I did a 50/50 mix of the two, LOL.

[SCCAForums]

I’ve been running the SuperCar 5w50 exclusively in our dedicated track SS 1LE.

Best regards,
Dave

[zapp]

Thanks! Sounds like the Supercar 5W50 should work very well as a dual purpose oil for a weekend & track car in warm weather

Wish we would have more precise specs from Mobile1 on it though.. :/

[Msquared]

Originally Posted by zapp

Thanks! Sounds like the Supercar 5W50 should work very well as a dual purpose oil for a weekend & track car in warm weather

Wish we would have more precise specs from Mobile1 on it though.. :/

I agree with all of that. If you're still daily-driving your SLE, then I would stick with 0w-40 for its much better cold-start flow. However, use X4 instead of Supercar in that weight: it's still Dexos R rated, but has significantly better 100C viscosity, HTHS, and resists viscosity breakdown better than Supercar.

OTOH, if the car is not cold-started daily and is just driven for fun and games, then 5w-50 should work well. I switched over now that I no longer daily my SLE.