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#4442805 - 06/27/17 01:15 PM GM recommendation: 15w50 for track driving
dparm Offline


Registered: 04/19/10
Posts: 13466
Loc: Chicago, IL
GM has some verbiage in the Corvette owners manual saying you should switch to Mobil 1 15w50 for track driving and then go back to Mobil 1 5w30 for the street. Logistically that is a headache and financially that is...unpleasant.

I am looking at my Performance Data Recorder (PDR) info and checking oil pressure + temp values to understand just how hard the 5w30 is being worked on the track. It's showing max oil temp of about 260 F, and oil pressures of 29psi (min) to 46psi (max). This was during a 30-minute session with ambient temps of 75 F, but I saw almost similar values on another day with 20-minute sessions.

Someone actually asked the chief Corvette engineer about this as part of his Q&A series on CorvetteForum.com:


descartesfool asked:
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 Porsches and GT-Rs 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?


Tadge answered:
GM Propulsion Systems has validated all Corvette engines to operate with the DEXOS 5W30 for all but the most extreme track conditions. We recommend the use of Mobil 1 15W50 when the vehicle is going to be used for high-temperature track operation as the higher viscosity range provides a greater degree of protection under the extreme stresses of that duty cycle. We like the extra lube performance in those conditions because, unlike some other manufacturers, driving on the track does not automatically void the warranty. However, daily driving use of the Mobil 1 15W50 on the street has not been validated, and as such we do not recommend its use where the operating temperatures can run lower. Some contributors to the thread correctly point out that few Corvette drivers operate their vehicles at extremely low temperatures, but as the manufacturer, we have to protect for that possibility. Another issue is that the 15w50 oil has higher phosphorus and ash content than we specify for factory fill. That is ok for track usage, but in long term street usage, those chemicals can compromise catalyst performance. As the manufacturer, we are expected to meet EPA emissions for a very long time. Lastly, the higher viscosity will also result in a small loss of fuel efficiency.

As for the Mobil 1 0W40, it was not available when we validated these engines and, in its currently available formulation, it also contains more phosphorus and ash than we specify. So, even if we validated the 0W40 for track use, we would still have to recommend reverting to a DEXOS 5W30 for daily street use.

Like all aspects of the auto industry, lubricants continue to improve over time. We work with Mobil and others to elevate the performance of their products and hence ours. We will continue to do that and when we have a better oil to ship in our engines or recommend for use on the track, we will do so.




So...thoughts? Reading between the lines seems to say that 15w50 is fine on the street as long as it isn't cold outside, and they don't test that because the fuel mileage would probably suffer meaning more gas guzzler taxes, but you may damage the cats over time.
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#4442813 - 06/27/17 01:22 PM Re: GM recommendation: 15w50 for track driving [Re: dparm]
drtyler Online   content


Registered: 01/04/06
Posts: 406
Loc: GA
I agree with your assessment.

I'd probably use either 15W50 or 0W40 for all uses, and not worry about the 5W30 dexos.

If your car won't see winter use in Chicago, the 15W50 should be fine.

Enjoying the new Corvette at the track more than the M3?


Edited by drtyler (06/27/17 01:23 PM)

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#4442821 - 06/27/17 01:26 PM Re: GM recommendation: 15w50 for track driving [Re: drtyler]
dparm Offline


Registered: 04/19/10
Posts: 13466
Loc: Chicago, IL
Originally Posted By: drtyler
I agree with your assessment.

I'd probably use either 15W50 or 0W40 for all uses, and not worry about the 5W30 dexos.

If your car won't see winter use in Chicago, the 15W50 should be fine.

Enjoying the new Corvette at the track more than the M3?



Yes, the Corvette is absolutely monstrous on the track. PDR data from yesterday showed 130mph and 1.4g!
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#4442825 - 06/27/17 01:31 PM Re: GM recommendation: 15w50 for track driving [Re: dparm]
Phishin Offline


Registered: 05/01/12
Posts: 2430
Loc: Indiana
If I owned a new Vette, I'd run a 40 or 50 weight without hesitation and never put 5w30 in it for any reason.
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#4442828 - 06/27/17 01:36 PM Re: GM recommendation: 15w50 for track driving [Re: dparm]
440Magnum Offline


Registered: 02/01/09
Posts: 8754
Loc: Texas
The answer looks like 0w40.
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#4442831 - 06/27/17 01:38 PM Re: GM recommendation: 15w50 for track driving [Re: 440Magnum]
dparm Offline


Registered: 04/19/10
Posts: 13466
Loc: Chicago, IL
Originally Posted By: 440Magnum
The answer looks like 0w40.


Not Dexos-certified, though the 15w50 isn't either...
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#4442861 - 06/27/17 02:12 PM Re: GM recommendation: 15w50 for track driving [Re: dparm]
turtlevette Offline


Registered: 12/24/13
Posts: 3569
Loc: Massachusetts
"we still have to recommended 5w30 for street driving"

He has to. Does he want to?
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#4442863 - 06/27/17 02:15 PM Re: GM recommendation: 15w50 for track driving [Re: turtlevette]
dparm Offline


Registered: 04/19/10
Posts: 13466
Loc: Chicago, IL
Originally Posted By: turtlevette
"we still have to recommended 5w30 for street driving"

He has to. Does he want to?




Yep, hence my "read between the lines" comment. They have economy and pollution targets to meet, plus Dexos certification is probably quite lucrative (they make $0.36/gallon, I think). Obviously, requiring an oil that will blow out emissions parts early/often will cost them a lot in warranty replacements, too.

It's amazing how GM will warranty the Corvette for track use, but they are very poor with their wording on some aspects of the track prep.
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#4442865 - 06/27/17 02:18 PM Re: GM recommendation: 15w50 for track driving [Re: dparm]
DriveHard Offline


Registered: 11/24/03
Posts: 1070
Loc: Middle of Iowa
I run 0w-40 all summer long in my Chevy 6.2L truck, and 5w-30 in the winter. If I owned a Vette, I would do the same.
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#4442868 - 06/27/17 02:23 PM Re: GM recommendation: 15w50 for track driving [Re: dparm]
userfriendly Offline


Registered: 06/03/03
Posts: 2630
Loc: LaFinDuMonde
Oil pressure may not change using a thicker oil due to the "smart" variable displacement and pressure oil pump.
What I find interesting, is put basically the same 6.2L engine in a 1500 Max-Trailer pickup truck, and the oil is 0W20 no matter what. (2014 and newer)
Which engine is working harder over a longer period of time, the Corvettes 'n Camaros, or the truck towing up a mountain pass on a hot day?
There are many choices between 5W30 and 15W50 that are just as good and don't cost an arm & a leg.
I would look at a CK-4/SN 15W40 or SAE 40, both with high flash points and HTHS's between 3.9 and 4.50.
True, there is a 7 year 100,000 mile warranty on emission equipment that would influence GM's engine oil recommendations.


Edited by userfriendly (06/27/17 02:25 PM)

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#4442869 - 06/27/17 02:25 PM Re: GM recommendation: 15w50 for track driving [Re: dparm]
oil_film_movies Offline


Registered: 06/13/16
Posts: 2569
Loc: MN
Originally Posted By: dparm

Someone actually asked the chief Corvette engineer about this as part of his Q&A series on CorvetteForum.com:
Tadge answered:
GM Propulsion Systems has validated all Corvette engines to operate with the DEXOS 5W30 for all but the most extreme track conditions.

As for the Mobil 1 0W40, it was not available when we validated these engines and, in its currently available formulation, it also contains more phosphorus and ash than we specify. So, even if we validated the 0W40 for track use, we would still have to recommend reverting to a DEXOS 5W30 for daily street use.


M1 0w40 "not available"? Means they couldn't get to a Walmart I guess... grin M1 0w40 came out in 1996. I can't believe he wrote that.

Actually, Corvette enthusiasts should be using Pennzoil Ultra 0w40 (Dodge SRT version) since it has 275 ppm of moly for extra protection during track usage, and Chrysler (FCA) recommends it for street usage too (low levels of Phosphorus for street use). Of course, I suppose you have to follow GM's idiotic 5w30-15w50 swap recommendations to keep your warranty valid in case something does happen, which is more likely since track usage is involved!

Also, with all this about M1 0w40 having too much Phosph, remember this oil is used in Mercedes & VW street cars every day, and their catalysts last just fine. In reality, the level of Phosph in M1 0w40 is only 20% more than an SN dexos1 5w30.

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#4442871 - 06/27/17 02:29 PM Re: GM recommendation: 15w50 for track driving [Re: dparm]
dparm Offline


Registered: 04/19/10
Posts: 13466
Loc: Chicago, IL
The car is under warranty, and GM will cover cars that get to the track, so I want to stick with their oils. I agree that 0w40 might be a better dual-purpose choice, but I'm not about to have GM deny a warranty claim if someting happens.
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#4442882 - 06/27/17 02:41 PM Re: GM recommendation: 15w50 for track driving [Re: dparm]
FordCapriDriver Offline


Registered: 10/22/15
Posts: 2384
Loc: Balearic Islands , Spain
If you drive your Vette on the track but not like a madman and also drive on the street, and you monitor the oil temps and oil pressure, M1 0W-40 would be ok, don't worry about the higher SAPS.
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#4442893 - 06/27/17 02:49 PM Re: GM recommendation: 15w50 for track driving [Re: dparm]
440Magnum Offline


Registered: 02/01/09
Posts: 8754
Loc: Texas
Originally Posted By: dparm
The car is under warranty, and GM will cover cars that get to the track, so I want to stick with their oils. I agree that 0w40 might be a better dual-purpose choice, but I'm not about to have GM deny a warranty claim if someting happens.


Why on earth do you think they wouldn't deny a warranty claim when 15w50 is in the sump? Its not Dexos-approved, either. They may warranty "track usage," but once you put 15w50 non-dexos in the sump (their internet forum recommendation notwithstanding), you're EVERY BIT as far off the map as you would be with 0w40. Their engineering advice to increase the viscosity at the track is good, but I think if you parse the language, they're being very careful to NOT say that you're still under warranty with 15w50. Yes, you're under warranty at the track. Just don't get caught with 15w50 in the sump if you make a warranty claim.

The paragraph about M1 0w40 is the most ridiculous thing I've read in a while. Not available?!? [censored]. Yes, it has more phosphorous and ash than Dexos oils, but SO DOES 15w50!!!

As I said before: I'd run 0w40 full time, and frankly GM is a bit insane for NOT just simply making that the recommendation for their higher performance engines the way FCA does with the 6.4 Hemi. You're in exactly the same boat you would be in using 15w50 if you had an engine problem while at the track with 15w50 in the sump.
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#4442897 - 06/27/17 02:54 PM Re: GM recommendation: 15w50 for track driving [Re: dparm]
440Magnum Offline


Registered: 02/01/09
Posts: 8754
Loc: Texas
Originally Posted By: dparm
The car is under warranty, and GM will cover cars that get to the track, so I want to stick with their oils. I agree that 0w40 might be a better dual-purpose choice, but I'm not about to have GM deny a warranty claim if someting happens.


Why on earth do you think they wouldn't deny a warranty claim when 15w50 is in the sump? Its not Dexos-approved, either. They may warranty "track usage," but once you put 15w50 non-dexos in the sump (their internet forum recommendation notwithstanding), you're EVERY BIT as far off the map as you would be with 0w40. Their engineering advice to increase the viscosity at the track is good, but I think if you parse the language, they're being very careful to NOT say that you're still under warranty with 15w50. Yes, you're under warranty at the track. Just don't get caught with 15w50 in the sump if you make a warranty claim.

The paragraph about M1 0w40 is the most ridiculous thing I've read in a while. Not available?!? [censored]. Yes, it has more phosphorous and ash than Dexos oils, but SO DOES 15w50!!!

As I said before: I'd run 0w40 full time, and frankly GM is a bit insane for NOT just simply making that the recommendation for their higher performance engines the way FCA does with the 6.4 Hemi. You're in exactly the same boat you would be in using 15w50 if you had an engine problem while at the track with 15w50 in the sump. The ONLY thing you're buying by using 5w30 on the street is that if you have an EMISSIONS system warranty claim, they can't (as easily...) blame the oil. That internet statement that they recommend 15w50 would probably go right out the window, though, if push came to shove on an emissions system warranty claim and they found out you had used it at the track. This is a case where I'd eagerly accept the risk. Its a sort of "self insurance." I'm going to lower my risk of an engine problem, at the slighly elevated risk that I might have to replace a catalyst out of pocket some time on the high side of 100,000 miles.
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