[BDCCruze]

I needed to change the oil in my ‘14 Diesel and was hoping to not pay dealer prices for the oil. At the Autozone site I put in my vehicle, and got a hit for Mobil 1 ESP Dexos2 5W-30. I ordered it for in-store pickup and when I got there they handed me a jug of Mobil 1 ESP 5W-30. Ummmmm… NO. It’s not Dexos2. In fact, not only did they have no Dexos 2 oil at all, they had no clue that you can’t use Dexos1 in its place and their system shows only one part number for Dexos1 and Dexos2. They did have a DexosD 0W-20, but I’d never heard of DexosD and the weight was wrong. I ended up getting my oil at a dealer because Dexos2 is nearly impossible to find elsewhere. Yes, the owner’s manual says that if you can’t find Dexos2 you can use an oil meeting the ACEA C3 standard, but it’s implied that it’s not ideal.

I’ve been an engineer for a long time, there are particular reasons why I have specific ideas about a few things (including oil) and I know a few people (I'm being vague on purpose, but I do live and work in Michigan if you want to guess about what that might mean). I asked a couple of them for confirmation and further explanation, and this is a summary of what I know:

• Dexos1 is for gas engines only, DO NOT use it in diesels.
• Dexos2 is for diesels. There are gas engines for which it was spec’d. The Dexos 2 spec started with ACEA C3, but has additional criteria for improved protection against varnish, sludge and foaming. Yes, you can use ACEA C3 if you have to, but for longetivity it’s best to use Dexos2.
• DexosD is a new standard that will be replacing Dexos2 for diesel applications.
• DexosR is a new standard that will be replacing Dexos2 for gasoline applications. It can also be used on applications that call out Dexos 1.

And of course, if the label doesn't say "Dexos-something", then it's not Dexos approved. Don't let the parts store guy tell you any different

A lot of folks have been talking about going to lighter weight oils (like the 0W-20 I found), or thinking that the difference between the HTHS viscosities of ACEA C2 vs C3 (2.9 vs 3.5 mPa*s) is not significant. Both of those are bad ideas for long term durability in this engine. I strongly suggest sticking with the oil spec'd out in the owner's manual if you want to maximize engine life.

GM Dexos

General Motors Oil Specifications - oilspecifications.org

ACEA Engine Oil Specifications - oilspecifications.org

I had a similar experience with I first bought my CTD in 2016. I was just looking around at different stores to see who carried Dexos 2 oil. The guy at NAPA said "this is dexos 2" and pointed to the bottle of Dexos 1 Gen 2 oil.

GM is doing away with Dexos 2 though and moving everything to DexosD. Right now, there are 2 licensed DexosD 5W-30 oils but both do not seem to be sold in the USA, but at least that proves 5W-30 can be DexosD certified. Based on the ACEA C5/6 spec of the 0W-20 DexosD oils, I didn't think it could be.

Nope. As temp drops from 100C, 0W-30 has a lower viscosity than 5W-30. This engine was not durability tested with 0W-30, it's not spec'd for it and I won't use it.

Again, I have a particular engineering background that informs my decisions here.

The manual says 0W-30 may be used in cold weather. The difference @100C is negligible between Mobil 1 ESP 0-30 and say Pennzoil Euro L 5-30. 12.5 vs 12 but the Mobil 1 does have better cold weather properties that some people want want. I've ran it in the winter a few times, but otherwise use the Pennzoil Euro L.

 

[BDCCruze]

Since my local Wal-mart doesn't have the Pennzoil Euro L 5W-30 any longer (it's gone from the shelf), I'll just switched to either of those Mobil 1 products. Probably the 0W-30 since it's right there on the shelf and is a 30 weight oil similar to the 5W-30 in the owner's manual.

You know what's funny, it disappeared from the shelf at my local Wal-Mart a month ago. I was just there a few hours ago and it's back and has 2 full shelf spaces to store like 12 at a time, before it just had 1 spot.

 

[BDCCruze]

It's summer, we're a long way from -20F. And not many people start their cars in the morning with the oil already at full operating temperature.

Right, but that's not what you said.

You said ...

0W-30, it's not spec'd for it

It is spec'd for it. I'm just clarifying for people who may be reading this that using 0W-30 in the LUZ is safe.

Additionally regarding your comment about it being summer and cars not starting out at full operating temperature, that's a little bit of a red herring. If you look at the numbers, the viscosity rating at 40C on the 0W-30 oil is closer to the viscosity of full operating temperature of 5W30 than than the 5W-30 is at 40C. Sounds like the 0-W-30 oil "cold" in the summer is at a better viscosity to be lubricating parts faster than 5W-30 is.

But overall, without seeing the viscosity index data, it's more difficult to compare the viscosity rating across a range of temperatures than simply 2 numbers on a bottle. Trying to compare the two, the W viscosity and summer viscosity are measured using different test, and to make it more difficult the winter grade testing varies in temperature per qualifying grade which makes it even harder to compare.

Finally, one huge thing you are leaving out but as an engineer you should know this - the viscosity ratings on oil have a range they fall into in order to be a assigned a specific grade. Oil being half a point different in viscosity at the same grade is totally acceptable. For example, anything between 9.3 and 12.5 on the cSt test @100C is considered SAE30. You could have a 0W-20 oil be .1 difference @100c from SAE30. I'd argue there's more difference between a 9.3 and 12.5 than a 9.2 and 9.3, but that's just me. And in fact, even oil from the same brand and same viscosity from 2 different batches will have a margin of error and measure slightly difference in viscosity ratings.

So it's a little bit more nuanced than you are making it out to be and someone well researched may be able to come to a conclusion that it is safe using even 0W-20 oil. i.e. a thick 0w-20 and a thin 5w-30 may be very close in performance. Though I personally would prefer to stick with 5-30 or 0-30 on my car.

 

[BDCCruze]

0W-30 is absolutely not spec'd for it, not in 2014 The owner's manual specs 5W-30. It specifically says to not use other viscosity grades, with the exception that you may use 0W-20 when ambient temperatures are below -20F (as I said in post #7).

Friend, you are looking at the Dexos 1 section. There is a separate section for Dexos 2.