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.

5W-20 Dexos-1 oil selection is very limited

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:

Background on Dexos

• 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.)^[3:1],^[4]

• 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.^[5] 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.

The switch to 0W-20

• 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.^[6] (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.^[7]

• 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.^[8]

Conclusions

• 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!