2022-12-29
This afternoon, a couple of friends and I went down a bit of a rabbithole while looking for Dexos-1 5W-20 motor oil for my 2017 (2nd generation) Chevy Volt.
The main takeaway: It’s easiest and best to use Dexos-1 certified 0W-20 (rather than 5W-20) motor oil in the 2nd generation (2016-2019) Chevy Volt.
Some more notes down below in case it’s helpful or interesting for anyone in the future.
The owner’s manual for my car gives these instructions:
Ask for and use engine oils that meet the dexos1™ specification. Engine oils that have been approved by GM as meeting the dexos1 specification are marked with the dexos1 approved logo. See www.gmdexos.com.
…
Use SAE 5W-20 viscosity grade engine oil. SAE 0W-20 may be used as an alternative.
2017 Chevrolet Volt Owner’s Manual, page 245
At the auto parts store, I was surprised to find that most brands of 5W-20 oil did not carry any Dexos-1 logo on the container. However, the 5W-30 and 0W-20 oils of the same brands immediately next to the 5W-20 oils had the Dexos-1 logo. Additionally, there was a mix of Dexos-1 Gen 2 and Dexos-2 Gen 3 logos.
I was able to find just one or two brands of 5W-20 oil with the Dexos-1 logo. Pennzoil had it, and I think maybe Castrol as well:
Adding to the confusion, the offical Dexos pages of licensed brands indicate that all of these brands have 5W-20 oil that do meet at least the Dexos-1 Gen 2 certification, if not Gen 3 as well.1,2 Yet we didn’t see these on the shelf.
So what’s going on here? We went back and did some searching, and here’s what we found:
Dexos is General Motors’ own engine oil specification (on top of the other industry-wide specifications).3
Dexos-1 is the main version for gasoline engines. (There’s a Dexos-2 that’s mostly for diesel engines, as well as a Dexos-D and a Dexos-R.)4,5
Dexos-1 Gen 3 is a more rigorous standard which supersedes Dexos-1 Gen 2. On September 1, 2022, Dexos-1 Gen 2 was phased out and the certifications were made obsolete.6 So the Gen 2 logos we saw were likely just old stock still on the shelf. For the Volt, which was made before Gen 3, we can use either Gen 2 or Gen 3.
Only a few GM vehicles seem to have ever used 5W-20 viscosity oil, at least in the past decade. The Volt is one of these few.
A December 2013 service bulletin instructed that several GM vehicles which originally only used 5W-20 could instead use 0W-20 oil.7 (The Volt wasn’t included here since the 1st generation didn’t use 5W-20, and the 2nd generation was launched a couple years after the bulletin was issued.)
With the switch to Dexos-1 Gen 3, most manufacturers opted not to get the certification for their 5W-20 oils, likely because there aren’t many/any GM cars that need this oil, especially after the above service bulletin.8
For the 2018 and 2019 model years, the Chevy Volt owner’s manual text was changed to remove the mention of 5W-20 oil. Instead, it only prescribes 0W-20 oil.9
0W-20 Dexos-1 Gen 3 oil will be the easiest oil type to find for the Volt, and is the only official recommendation for model years 2018-2019.
Dexos-1 Gen 2 is now obsolete, and should disappear from stock soon.
A few brands have 5W-20 oil with the Dexos-1 Gen 3 certification, apparently catering to the 2016-2017 Volt (and select other GM models) owners who haven’t heard about the switch to 0W-20.
Honestly, I think 5W-20 oil which previously carried the Dexos-1 Gen 2 certification is probably just fine to use (they likely haven’t changed the formulation), but you might as well just get the 0W-20 with the Dexos logo.
Thanks to Corey and Frank for digging into this with me!