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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 phosphorous 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 phosphorous 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.
Nice reply. A note also that Mobil 1 0W40 has just been re-formulated and they have added a code called FS (Fuel Saving?) and they no longer list approvals for BMW, Nissan GT-R and others that were previously listed on the bottles. Porsche and VW and Mercedes approvals are still there. Viscosity at 100 C has been lowered a touch, but it has more boron in it than before for improved lubricity, as well as other changes. Like Tadge says above, lubricants continue to improve over time, and fuel economy and oil change intervals are major drivers of changes to oils.
So will not switching back to standard weight lead to a voided warranty? He only went so far as to say not recommended, since they haven't validated it.
Funny that he said the Mobil 1 0W40 was not available for testing/validating on the C7 engines. It is the factory fill on all Porsches and my 2009 GT-R which I bought in 2008, and was the factory fill when the 2008 GT-R was released in Japan in 2007. So there is no way the oil was not available, as that is over 9 years ago. It is really nice on Porches and GT-R's that you never have to change the oil for either track or road use. I wonder how many people would actually change the oil back and forth on Corvettes for every single track event. I suspect virtually no one from the entire group of guys who track their Corvettes regularly.
Funny that he said the Mobil 1 0W40 was not available for testing/validating on the C7 engines. It is the factory fill on all Porsches and my 2009 GT-R which I bought in 2008, and was the factory fill when the 2008 GT-R was released in Japan in 2007. So there is no way the oil was not available, as that is over 9 years ago. It is really nice on Porches and GT-R's that you never have to change the oil for either track or road use. I wonder how many people would actually change the oil back and forth on Corvettes for every single track event. I suspect virtually no one from the entire group of guys who track their Corvettes regularly.
He did mention in the 0W40s current formulation which hints at a recent change in the oil.
The main criteria for switching back to the 5W30 is they are concerned about fuel mileage issues with the EPA and the affect of 15W50s additives on the duration of their cats. If they recommended the oil for street driving they would have to address the cat durability issue and retest the fuel mileage and possibly get hit with more gas guzzler taxes. For most owners that most likely means you don't have to rush off to an oil change place to pull the 15W50 out of the car when you get back from the track. He can't say anything definitely due to regulations but can explain their reasoning and let owners read between the lines.
So sounds like reading between the lines it would be fine to leave the Mobil 1 15W50 in for street use after the track as long as not used in cold temps. Anybody know how cold we are talking? Living in Orlando, I doubt I have to worry about it, though.
Other than that, just a minor degradation in fuel economy and emissions.
He did mention in the 0W40s current formulation which hints at a recent change in the oil.
The main criteria for switching back to the 5W30 is they are concerned about fuel mileage issues with the EPA and the affect of 15W50s additives on the duration of their cats. If they recommended the oil for street driving they would have to address the cat durability issue and retest the fuel mileage and possibly get hit with more gas guzzler taxes. For most owners that most likely means you don't have to rush off to an oil change place to pull the 15W50 out of the car when you get back from the track. He can't say anything definitely due to regulations but can explain their reasoning and let owners read between the lines.
St. Jude Donor '13,'14,'15,'16,'18,'19-'20,'22,'24
Originally Posted by slickstick
So sounds like reading between the lines it would be fine to leave the Mobil 1 15W50 in for street use after the track as long as not used in cold temps. Anybody know how cold we are talking? Living in Orlando, I doubt I have to worry about it, though.
Other than that, just a minor degradation in fuel economy and emissions.
Any oil temp chart should show you what you need to know:
Any oil temp chart should show you what you need to know:
Ambient Temps are a poor predictor of Max oil Temps for those who track this car. 15w50 any time of the year on stock cooling system unless you want to hold your rod bearings at the event.
Great question and great response. No easy solution but to read between the lines indeed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16,'17,'18-'19-'20-'21-'22
Originally Posted by Snake.Oiler
Any oil temp chart should show you what you need to know:
So my 2016 Silverado with the 5.3L V-8 should NOT be using the recommended 0W-20 oil here in Miami, where it RARELY gets down to 10 degrees C. This direct injection, cylinder-cutoff engine uses a lot of the same components and logic as the LT1 in the Corvette, so there is no reason not to use 5W-30 in place of the kerosene that GM wants it lubricated with, to meet fuel economy targets.
Mobil 1 15W50 will eventually cause damage to the cat's
Mobil 1 15W50 will reduce fuel efficiency
And since virtually any oil is too thick for best lubrication when you first start in the morning, 15W50 almost certainly produces more wear in ordinary driving than 5W30. And if you're not running high oil temps like at the track, probably doesn't protect any better at normal driving temps.
Everything is a compromise...
Some explanation is required for dexos. Mobil 1 5W30 is dexos compliant. Dexos is not an oil brand or model. It is a GM specification that any oil manufacturer can choose to design an oil to.
Any number of oils are made in 5W30 viscosity and are dexos compliant, such as Pennzoil, AC Delco, Quaker State, etc.
You can count how many oils are dexos compliant by looking at the list on this page. Judging by the very large number of oils meeting the spec, it is not impossible for any manufacturer to do it: http://www.centerforqa.com/dexos-brand1/
Here is some interesting info on dexos compliant oils:
"The GM dexos spec was merely a year or so ahead of the oil industry’s new GF-5 oil spec. GF-5 will replace GF-4. These specs are developed by the International Lubricants Standardization and Approval Committee (ILSAC) with input from automakers, oil refiners and additive makers.
For those more familiar with the American Petroleum Institute (API) rating system, the new ILSAC GF-5 will carry an API “SN” label.
The move to synthetic oil was coming anyhow. GM dexos just got the jump on the rest of the industry. The new GM dexos, ILSAC GF-5 and API SN oils are superior in almost every way to conventional, non-synthetic motor oil.
The GM dexos oil has one spec that ILSAC and API labeled oils do not have. This is quite important! That dexos requirement is for better resistance to aeration, which is the whipping of air bubbles into the oil. Engines with variable valvetrain (variable camshaft timing) technology use engine oil as a hydraulic fluid to move components in the engine, i.e., hydraulic lifters.
If air bubbles are in the oil, the lifters will not act as fast as the engine controllers expect. On the mild end, this can limit engine performance and economy. On the extreme end, this slow response can throw a MIL or DTC check engine code. Engines with a variable valvetrain timing are very common"
And Conocophilips published a chart comparing test requirements for GF-4, GF-5 and dexos.
03-24-2016, 10:38 AM
[ANSWERED] Changing oil type for the track and for road use
This direct injection, cylinder-cutoff engine uses a lot of the same components and logic as the LT1 in the Corvette, so there is no reason not to use 5W-30 in place of the kerosene that GM wants it lubricated with, to meet fuel economy targets. 
