Mobil 1 15W50, 6k mi OCI, 15.6k mi, C7 Corvette Z06

[Emperors6]

All mileage is in kilometers not miles.

Notes from oil slip: "30 hours of track time + street use. This is the same oil as last UOA, the previous was just a sample. How much longer could I have run it? The OLM was at 24%."

Previous fill was Mobil 1 15W50.

 

[buster]

Looks good. Still life left. I noticed on your RL UOA you used 2qts of makeup oil?

 

[Emperors6]

Yeah, I always added 0.5qt at the track as recommended in the manual. It seemed to burn off, so I would add more at the next track event. I haven't seen burn off with M1 15W-50.

 

[buster]

Interesting that you had significantly less oil consumption with the M1 compared to RL. RL held its viscosity a bit better, which I'm not surprised as that's RL's greatest attribute.

 

[tundraotto]

Red Cap Mobil 15W-50 was my favorite oil for all my smaller engines - don't like the silver cap new version nearly as much because of the reported wet-clutch issues.

Regardless - It seems to have served your Vette very well....good stuff.

 

[A_Harman]

Manganese? What's the source of the Manganese on the last 4 samples?

What did you find the source of the misfire to be? Did it go away with the switch to M1 15w50, or were there other changes made as well?

M1 looks like it's doing a fine job.

 

[Emperors6]

Source of misfire was probably the air post supercharger to be too hot. We upgraded the cooling, and it's reduced it a lot, but not completely gone if it's close to 90F outside. I'm going to switch to a 2017 supercharger which has better positioned heat exchanger in the plenum and a bigger plenum volume.

 

[Emperors6]

Oh, the source of manganese might be the octane booster I added at some track events. It helped (somewhat) with the misfires, just not fully. Anyways, I stopped using it, since the cooling upgrades we did reduced the misfires at the track. Doing some further upgrades to hopefully have no more misfires in long track sessions.

 

[A_Harman]

I think the LT4 engine goes pig-rich when the intake manifold temperature gets to ~180F, so it may be rich misfire, with Air-Fuel ratio somewhere below 10:1.
That's so rich that the engine is down about 50 hp.

 

[Emperors6]

I see. When I get a chance, I'll take a look at the misfires counters and the IAT temperatures around that time. Anyways, I'm putting a larger DeWitts 70mm radiator, and seeing how that does. If not, I can always upgrade the engine oil to air cooler even more!

 

[A_Harman]

I think the ultimate solution would be to get rid of the air-water intercooler and the chassis-mounted intercooler radiator, then put an air-air intercooler on it.
I don't know of anybody who has designed such a thing yet.

 

[Geoff]

Interesting report - thanks. I think I will use 15w-50 most of the year here in Austin.

On your misfires. I think its oil in the intake. Need a catch can. Not as straightforward of an install with the LT4. I am weighing for my LT4. With my LS3 Camaro, the catch can cleaned up the pop pop when lifting, idle smoothed out, and I could tell the engine would stay in "premium" fuel mode with advanced timing. PCV intake oil mist reduces octane. Exhaust tips were clean too.

With my new ZL1 I will likely install a catch can. Still researching for track use pressures.