I definitely would not recommend doing that. 15w50 is not going to flow anywhere near as well as 5w30 when it's in the 20s out. And honestly, you don't need to run a 15w50 for everyday driving, save that stuff for the cars that are being run hard exclusively on the race course.

 

The manual says (Page 10-15):

"SAE 5W-30 is the best viscosity
grade for the vehicle. Do not use
other viscosity grade oils such as
SAE 10W-30, 10W-40, or 20W-50."

 

And the change was actually MY2011.

 

If you take your car to a GM dealer for an engine oil change and your car's engine oil specification is Dexos1, your car's engine oil will be filled with AC Delco Dexos1 engine oil.

I'm not saying you are wrong, just saying there is a GM Dexos1/2 oil.

 

Not disagreeing with you. Your comment earlier was there was a Dexos brand. I just wanted other folks not knowledgeable about Dexos to understand that Dexos is not a brand, like Mobil1, but rather that Dexos is a standard like SAE SN or GM4718M which was the old corvette STANDARD that GM required for corvettes. I know it's semantics but folks can get easily confused by the Dexos issue.
You are right, there is an AC Delco brand oil that is rated Dexos 1/2.

 

This is a FACT--The 2014 C7 Corvette comes from the factory with Dexos 1--5-30 weight--FACT Dexos 1 is MOBIL !-identical in everyway!!

 

Your facts are completely wrong. The Corvette comes from the factory running AC Delco semi synthetic oil, which is not Mobil 1 at all. Dexos 1 is simply a specification, not a brand of oil, and many oils out there qualify for the Dexos 1 spec.

 

I thought Dexos1 was a Starbase in the Beta Quadrant

 

The way I understand the term dexos is this: (Please add corrections where I get it wrong)
A few years ago (3 or 4), GM decided for several possible reasons the then current standards for oil did not fit with the direction that GM was going with their vehicles. That decision was part technical, part political, and of course part financial.

GM called their new engine oil spec dexos. At this point as far as I know there are 2 flavors of dexos: dexos 1 for gas engines and dexos 2 for diesel engines.

Any company can create oil that meets the dexos specification, but if they want to carry the “dexos approved” label then the company has to take a license with GM.

At first the other oils companies balked because they saw it as a money grab by GM, resulting in an initial price increase that would be passed along to the consumer. But if you do a quick search you’ll see more and more companies are taking out licenses so they can display the dexos approves label.

 

note that the manual states that with stock tires, you are at risk at anything below 40 degrees (f). regardless of oil, you should not be out until summer, or if in florida, all the time, then check on oil..

 

Been using Mobile 1 since my new 260Z in the mid '70's and still will but it may not be the old, 'full synthetic,' quoting:
"Mobil 1 was originally group 4. Castrol started marketing a group 3 oil as being fully synthetic, on the basis that the severe hydrocracking of group 3 scrambled the hydrocarbons enough to call them synthetic in the sense that the resulting molecules are not naturally occurring. Mobil sued them, but lost. So now, in the USA, both group 3 and 4 oils can be advertised as being fully synthetic. As a result, even if the oil is advertised as fully synthetic, unless they specifically say it is group 4 (Mobil 1 does not), you do not know how much, if any group 4 oil it contains. Since they lost the lawsuit, Mobil refuses to answer the group 3 vs 4 question, so it is pretty clear that rather than label Mobil 1 as group 4 and continue making it as they originally did, they are using at least some group 3 base in Mobil 1. Just like any other oil that is labeled fully synthetic, but not labeled group 4, you cannot rule out the possibility that it is 100% group 3. Before you start screaming that Mobil 1 is no longer any good, remember that it still meets 4718M spec."
For what it's worth.

 

Thanks for a response I can understand not being a chemist.

 

"Your vehicle calls for an oil that is approved to the GM dexos 1 specs. Both Mobil 1 Extended Performance 5W-30 and Mobil 1 5W-30 are officially dexos 1 licensed products. For track events or competitive driving use Mobil 1 15W-50. "

 

The Mobil 1 15W-50 recommended in the C7 owner's manual for track use does not have a Dexos 1 approval. Just bought a bunch of 5 quart jugs at Walmart for my track days next spring, and while I was there I looked over all the labels of Mobil 1's different offerings. Easy to see which ones have Dexos 1 amongst all the different approvals listed for each grade.

Why GM thinks you need an oil passing their Dexos 1 spec is a mystery to me, aside from marketing. What do people think will happen to their C7 engines if you use a synthetic oil of the right grade that does not meet the Dexos 1 spec. Instant failure? Worn out bearings or cylinders after a year? I have never had any engine in any car break or wear out since I have been driving on track, since 1997. Not expecting any failures soon. I have standardized all my cars on Mobil 0W-40.

Here is one comment I found about GM's requirement's for oil: http://autos.aol.com/article/gm-engine-oil/
"The dexos oil also has some unique properties that General Motors engineers required. One characteristic is better resistance to aeration (the whipping of air bubbles into the oil). Some GM engines with variable camshaft timing use engine oil as a hydraulic fluid to move components within the engine. If air bubbles are in the oil, components actuated by engine oil will not move as they were designed to, limiting engine performance and efficiency."

and this: http://themotoroilevaluator.com/memb...#axzz2rW2MZ44X
"It’s of little consequence, though. If you’re looking for dexos 1 quality for your non-GM vehicle, just go with a high quality synthetic oil. You’ll be getting all the protection and performance you need, every bit as good as any dexos licensed oil. Just know that when I say a “quality” synthetic oil, that is not a term that I would apply to ALL “synthetic” oils."

 

Well written.....I would like to see any case where a non DEXOS oil, of proper viscosity, has done damage and chev blamed it on the oil.....I think it's marketing too, there is nothing exotic about the LT1 that it NEEDS a DEXOS oil...and I doubt that the local dealer would do a blackstone test to check on you.....

 

I recall reading somewhere that to be able to use the "meets DEXOS label" you have to pay Chevy a fee! Not sure if that is accurate, but could explain it!

 

Wesson oil. If its not available, Crisco Sunflower is an acceptable alternative.

 

Found the reference, recall some oil companies were not going to pay, like Mobil! Here is an abstract of key points in the article:

"GM has switched the licensing fee on its Dexos global engine oil from a royalty on every gallon of Dexos sold to a flat annual fee based on an oil company’s market share. Originally, licensees were to pay a royalty of 36 cents on every gallon of Dexos sold.
Also of interest, API also gets an annual royalty of $0.002 per gallon to show API’s donut and/or starburst trademarks for volumes exceeding 1 million gallons a year."
I could not define the new GM deal from the information provided, as it was based on market share after an intial fee and started at some minmum volume. Sounded like airline pricing!

 

I have some Mobil 1 sitting on the shelf that is 3 years old and does not have the Dexos rating. Can it still be used in a C7?

 

Hmm. You get 2 years of free oil changes for a C7, by then it will be 5 years old! Don't know what the shelf life is! Think I would use it in another car!