descartesfool

What is the effect of changing from Dexos compliant 5W30 to Mobil1 15W50 for the track and back for road use? Some cars which are used on track a lot such as Porsche's and GT-R's recommend Mobil 1 0W40 for all uses, with no changes required when driving on track. Would this oil be fine for track and street use in the C7? What are the negative effects of leaving the 15W50 after track days and driving on the road, and at what temperatures is it an issue, hot or cold? Some of these oils have higher ZDDP levels, and current formulations have much lower levels, so how does this affect catalytic converter life; is it a 100,000 mile issue or is it much shorter? And how about sludge formation in the engine when running at very high oil temps on track? Another chief engineer of a different car said the Mobil 1 0W40 was the best at resisting sludge formation inside the combustion chamber, and a Mobil 1 rep at their booth at the PRI show told me that particular 0W40 oil was their "best" oil, so it would be nice if we could safely use it all the time for track and road use. I suspect very few people who tack their cars take the 15W50 out after every track day.

5thGear

Great question. Will get my vote

CPhelps

I'm guessing they want the protection from the 15W50 for track use, but the fuel mileage from the 5W30 for road use.

Clairvoyantwolf

Good question

jvp

That's partially it. The lower 5W is beneficial in colder temperatures. Remember that these cars have to be able to be driven in very cold temperatures (funny that their OEM tires can't). The higher 15W will provide less viscosity in the colder temps than the 5W does.

Now, while you might not consider driving your Corvette in ice cold temps, that doesn't change the fact that GM validates them for it. Thus the 5W.

SBC_and_a_stick

Good question.

LV2CRNR

Actually the 15W provides HIGHER viscosity, viscosity is a measure of a fluids resistance to flow. This is why Mobil 0W-40 is such a great oil, at colds temps it is relatvely thin so it flows easier but still has a higher viscosity at operating temps so can handle the high performance aspects of driving. Plus is has higher ZDDP to boot. Obviously 15W-50 is better for a dedicated track car but 0w-40 is the best all around oil.

The problem with oil is not that it thins out as it gets warmer, its that it gets thicker as it cools down. Have to think like a petroleum engineer

SBC_and_a_stick

That was my intuition as well. Best guess is that GM went with the thickest Mobil 1 oil available for track use to prevent engine failure. They would have went with a 60 weight if they could haha.

KnightmareCS

Mobil 1 15W-50 has higher ZDDP than the regular 5W/10W; not sure about 0W levels. I know the SBC crowd recommends 15W for performance builds because of this.

Gary '09 C6

this is a good question +1.

b-t-w, I believe the M1 0W-40 also has slightly higher ZDDP content than the M1 5W-30

KnightmareCS

Here you go ladies:

Specs for all Mobil 1 oils:
https://mobiloil.com/~/media/amer/us...pecs-guide.pdf

Source:
https://mobiloil.com/en/faq/ask-our-...r-classic-cars

700horsepower

Unless you plan on driving your Corvette in sub freezing temps (which you should not have to do) just leave the 15w50 in it and forget about it. It has more of the good stuff in it, wont affect the mileage and will offer more protection under high load (high cylinder pressure) use. Every off road all aluminum racing engine that I know of is recommended to use 15w40 or 15w50 as the extra clearances naturally in a hot all aluminum engine can use the slightly heavier viscosity oil.

5thGear

I hope this question will get another chance for voting

descartesfool

One of the main points is whether or not you could just use Mobil 1 0W40 for every use, and not have to bother changing up to 15W50. 0W40 is the oil used by many cars for both track and road use with no requirement for chaning betwen lighter an thicker oils for road and track.

jvp

This one accidentally got lost in the shuffle. I'll remember to put it up next time around.

5thGear

Good point.
I would revise the original post and make this question direct and clear before it goes to voting.

Thejoyofdriving

Excellent question. I have heard the warranty is voided if you don't change the oil for track use.

Bill Dearborn

I vote for this one also. 50 years ago Multiviscosity oils were just coming to the marketplace. The usual manufacturer's oil recommendation before that was in the spring, summer and fall we ran straight 30 weight and in the winter we ran 10 weight. Of course we changed oil every 3 months back then and the engines weren't built as tight.

My 65 and 68 Old's required either 10W30 oil year round or the 10 in winter and 30 in summer combo. Oil consumption with the multiviscosity was about a quart per month but with the straight 30 weight I could go 3 months without adding.

Bill