The Dexose Oil Specification - 2011 Chevrolet Cruze Long-Term Road Test

2011 Chevrolet Cruze Long Term Road Test

2011 Chevrolet Cruze: The Dexose Oil Specification

May 23, 2011

Cruze Owners Manual.jpg

The recent oil change on our Chevrolet Cruze sparked some debate as to whether or not it needed synthetic oil. It was difficult to get a clear answer on this, but after some extensive research, I was able to find something. The GM branded Dexos oil that will be used in the dealer bulk tanks and sold over the parts counter is a synthetic blend. But if purchased from another manufacturer, it can also be a full synthetic. Sound confusing? Let me explain.

The photo above was taken from the owner's manual. The manual only says that the oil needs to be Dexos certified 5W30. In fact, there is no mention of the word "synthetic" anywhere in the owner's manual. The official "about Dexos" page didn't mention synthetic either.

Dexos is an oil certification standard created by GM to consolidate its recommended oils. It is comparable to the upcoming ILSAC GF-5 standard -- the one to which the entire oil industry will have to adhere. According to GM, the Dexos1 oil specification will decrease harmful piston deposits by up to 28 percent and improve fuel efficiency by up to 0.3 percent compared to the ILSAC GF-4 specifications. Dexos compliant oil is higher quality oil, but it isn't always fully synthetic. GM licenses the Dexos certification to motor oil manufacturers that can then choose to offer a full-synthetic variation, as long as it meets the requirements. All 2011 GM models and newer will use Dexos1 branded oil. Dexos2 is for diesel vehicles.

In the link that sodaguy posted, Mobil1 full synthetic is listed as one of the alternates that can be used in the event that Dexos1 is not available. While they haven't been formally tested, fully-synthetic, non-Dexos oil is listed because it meets and may exceed the Dexos requirements.

Tom Read, a GM powertrain technology representative, says that the term "synthetic," has different meanings depending on the oil marketer. "The use of the term "synthetic" with engine oil is used broadly and not standardized in the industry. However, Dexos would certainly qualify in the commonly understood definition of a synthetic blend oil," says Read.

If you go to the Dexos licensed brands page, you'll find that both non-synthetic and synthetic oils are listed. Now take a look at the second line, and you'll see "ACDelco Dexos1 SAE 5W30," which is supplied by General Motors. This is the oil that will be supplied to the dealers.

Read says that GM is in the process of distributing and educating its dealers about this new oil standard. But it takes time to get the message out. I found this out for myself when I called the parts departments of a few local Chevy dealerships. Most of them had never heard of Dexos and couldn't tell us whether or not Dexos was a synthetic oil. The ones who had heard of it said that it cost about $7 per quart -- a far cry from the $2.50 per quart on our recent bill. When I called the parts department of the dealer that had performed our oil change, it did not even have the oil in stock. I then knew for sure that our Cruze was not filled with Dexos oil.

I told our service advisor that we had reason to believe that our Cruze was not filled with the proper oil and showed him the Dexos page from the owner's manual. And as fate would have it, an internal dealer memo about Dexos was sitting on his desk. The service advisor referred to Dexos as a synthetic blend. He told me that the dealership had recently ordered a batch of Dexos oil and that the service department would replace our oil as soon as Dexos was in stock. He assured us that since it was that dealership's policy to fill all cars with a synthetic blend, we would be OK in the meantime and that our warranty would not be compromised.

These mix-ups are bound to happen when well-established standards change. We suspect that this kind of thing might have happened at Toyota dealerships, too. That company is slowly phasing in full-synthetic oil in many of its models.

On a final note, we asked Read what would happen if a person used a conventional 5W30 oil with the API starburst symbol (as per the owner's manual) for an entire oil interval:

"If a customer uses a non-licensed engine oil that is simply ILSAC GF-5 quality, they will not enjoy the benefits of using a Dexos licensed product. Those benefits could include better low temperature performance, cleaner pistons, better aeration performance, etc. This could be especially important as the engine oil ages. Furthermore, with the extensive licensing and quality monitoring program in place, the customer can be sure that the Dexos licensed product they are using actually meets that performance level."

If you own a 2011 or newer GM vehicle, I suggest checking with your dealer to make sure they give you the proper oil.

Ron Montoya, Consumer Advice Associate @ 10,175 miles

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