In a couple of threads, a discussion of oil ratings came up. The 2023 Owners Manual says use engine oils that meet the dexos R specification. The previous 2020-2022 manuals specify dexos 2. All the manuals say "see gmdexos.com". That site lists oils that are licensed under each spec. There are 4 0W40 oils listed that meet the dexos 2 spec. Only one oil is listed under the dexos R spec, the Mobil 1 Supercar 0W40. Folks on the forum said that the dexos R is just repackaged dexos 2. I looked for some official documentation that says that. Edit - see post 13 below that answers this. Also looked for something official that said dexos 2 could be used in place of dexos R, or dexos R could be used in place of dexos 2. I found many sites that said that , but none official gm or mobil 1 statements. There was a site called dexossubmission or something like that. Apparently it used to include some wording to that effect. But that wording was taken down, and can only be viewed in the cached version. So, I contacted Mobil and asked about it.

These are the questions I asked:
Question: 1) Are the dexos 2 and dexos R specifications the same? 2) Are the new "Mobil Supercar 0W-40" and the "Mobil 1 ESP Formula 0W-40" identical? 3) The 2023 Corvette Owners Manual recommends only motor oil 0W-40 meeting the dexos R specification. Can the previous recommended oil (for 2020-2022 Corvette with LT2 engine) , 0W-40 meeting the dexo 2 spec be use in place of that?

And, here is the response:

"Thanks for writing to us. DexosR is superseding Dexos2 in high performance gasoline engine applications (like the Corvette), only. Dexos2 is not going away, as it is still the standard for GM's "passenger light diesel" engines found in models like the Colorado/Canyon trucks, a few model years of the Cruze, and in the Equinox.
​

In earlier model years listing Dexos2 in the manual, Dexos2 licensed 0W-40 oils are still safe to use until the supply runs out. If your 2023 manual ONLY lists DexosR, I wouldn't risk giving anyone a loophole to void your warranty.

If I can help with any other questions, please respond to this email or call me at 1-800-ASK-MOBIL (800-275-6624).


Thank you for choosing Mobil,
Jim
Mobil Help Desk Team"


AND THIS IS FROM THE 2023 MANUAL

 

It sounds like you can use either dexos2 or dexosR in the 2020-2022 C8s, whichever you prefer depending on price and availability. But, technically, you should only use dexosR in 2023s because of the way the documentation is worded if you want to avoid potential warranty problems. From a practical aspect you could also use dexos2 in 2023s because they have the same engine as the 2020-2022s.

0W-40 dexos2 may become scarce if not many diesel engines use that weight.

 

I find it humorous the you correctly used the GM registered trademark, dexos as required with a small “d!”

Assuming you quoted “Jim” from Mobil correctly he incorrectly used a capital “D!”

Their trademark attorniies will be all over his butt!

 

That's the response I would have expected from Mobil 1 (except for the part "...I wouldn't risk giving anyone a loophole ..." if that is a direct quote of/from Mobil, and I'm not doubting you that it is).

In a long-ago gen, the LS3 came out w. a specific oil type (I think it was GM4718M for Mobil 1). It was a departure from prior recommended motor oil use and was toward the beginning of the "Dexos" name. Other brands of full syn oil eventually got the GM designation besides Mobil 1. It could happen with the C8.

 

Until the Dexos R labeled Supercar 0w40 hits the shelves in full, the Dexos 2 ESP Formula 0w40 is fine to use.

 

Yes it was a direct quote. I bolded some of the text in their response. Here is a clip directly from the email I received. Noteworthy to me is that he did not say they were the same, even though I specifically asked that. He said that dexos R supersedes dexos 2 in high performance performance gasoline engines like the Corvette. I think also his other remark about what to use if the manual only recommends dexos R is understandable. He can't actually speak for GM regarding the use of something with spec other than what is recommended in manual. I wonder if the dealers got anything from GM (in writing) on this subject.

 

I was fairly certain it was a direct quote that you used. In the past Mobil hasn't been quite as definitive altho still very helpful. It wouldn't surprise me that they came to a new understanding that what they decide (and design) with GM for their vehicles requires both parties to specify the same oil and not stay quiet, say different things, or waffle about what can be used, and what should be used. The part about "...until the supply runs out..." (referring to dexos2 0W-40) is also illuminating and a piece of information that I doubt I've seen before. It's refreshing. Thanks for getting the info.

 

I imagine they are not the same. Dexos2 was a specification for GM diesel engines that GM started using for gasoline engines. The dexosR specification probably doesn't have requirements for things that only apply to diesel engines and perhaps added some things that apply only to gasoline engines.

 

Without seeing the details on the specs we'll never know, but my suspicion is they came up with Dexos R because people were confused over using a Diesel spec oil in their LT2, and there's no change beyond the name. I seem to recall an article that talked about that. In any case, if Dexos 2 is fine for the '20 to '22, it's going to be fine for the exact same engine in the '23. I'm willing to bte dealers are still using the Dexos 2 version when '23 comes in for a change.

 

The ironic thing is the only current DexosR oil is exactly the same formulation as that same oils Dexos2 name and formulation so that becomes moot for now.

I do hope the esp x3 and other better dexos2 oils also become DexosR approved for the 2023 plus folks

 

The dexosR specification may have enhanced requirements to lengthen the life of gasoline emissions components. I know that vehicles exported to Europe have particulate filters on the exhaust system, something we don't have here on gasoline engines. I don't know what the warranty requirements are in Europe for the emissions components but you can bet that GM wants to make sure they last the length of the warranty.

 

Why do people on his forum always second-guess the words of wisdom put down by the engineers at GM in the user manual? What are they looking to accomplish?

 

I want to add to this thread something that was posted by bhvrdr in another thread, that answers one of the questions I raised in the OP. I had not seen this before, from an "official" source. This is from Mobil and says the "name" of the advanced synthetic motor oil for the new Corvette, "originally called Mobil 1 ESP Formula 0W-40.. ..is changing to Mobil 1 Supercar 0W-40".

 

What's the oil spec for the Z06?

 

5W-50 dexosR

 

I believe that this new R designation is to help with issues created by the direct injection of fuel in these vehicles. It creates an ash deposit that wears engine components prematurely. These dexos 2 and R suspend the the ash in the oil and prevents them being deposited on components. If you put minimal mileage say 3000 miles a year and change oil yearly. I believe any 0W-40 (quality) would be fine.

 

The R spec is nothing but marketing. Mobil has confirmed, in writing, that ESP 0-40 and "Supercar" 0-40 are exactly the same oil. Only the name has changed.

 

Correct, only the name has changed. Product even has the same UPC as the "old" version.

 

There are (or were) at least three different Mobil 1 0W40 dexos2 oils with different names, and different specifications. Those names are ESP X3 0W-40, ESP 0W-40, and ESP Formula 0W-40. Note that in the last one, the word "Formula" is part of the name of the oil. The oil that was "rebranded" as Supercar 0W-40 was the ESP Formula 0W-40. ESP 0W-40 (if its even available) and ESP X3 0W-40 are different oils.

 

https://www.gmdexos.com/brands/dexosr/index.html

Seems to say generic mobile 1 meets Dexos R specifications

What do you guys think??