Home News Worse MPG! 2021 Chevy Silverado 1500 4WD with Duramax sees big drop

Worse MPG! 2021 Chevy Silverado 1500 4WD with Duramax sees big drop

Worse MPG! 2021 Chevy Silverado Duramax diesel 4wd sees big drop
The Chevrolet Silverado’s 3.0L Duramax inline-six turbo-diesel engine sees a drop in fuel economy ratings for 2021. (Photo courtesy Chevy)

In a surprising move, the 2021 Chevy Silverado 1500 Duramax diesel will see a big drop in the stated MPG ratings versus the prior year, and nothing significantly changed from the 2020 model.

So, what’s up?

GMAuthority.com discovered this news after carefully examining the stated MPG numbers for the 2021 models. They noticed a pretty big difference for the 4WD version of the pickup versus the prior year.

Specifically, they found:

GM Authority reached out to Chevy and got the following reason for the drop:

“The 4WD 3.0-liter configuration went up in its test weight class, which led to slightly reduced fuel economy to 22 city/26 highway/24 combined. The 2WD configuration remains best-in-class with 23 city/33 highway.”

Huh? Confused? Let us explain.

How EPA testing works for trucks like 2021 Chevy Silverado 1500 Duramax diesel

First, GM Authority followed up and got this additional tidbit: It was a “higher-contented truck being tested based on production schedule.”

Unfortunately, GM Authority didn’t really understand what this meant and closed with people won’t see much difference in real-world testing.

This is the wrong conclusion, here’s why.

The MPG estimates come from Environmental Protection Agency (EPA) testing, which GM conducts on its own vehicles. Basically, the automakers self certify their own results and report them to the EPA. The EPA can — and has — done spot testing to make sure the automaker is, well, telling the truth.

Part of this testing allows automakers to pick the vehicles they want to rate for the EPA based on what they think will sell. For example, if GM thinks its best-selling Silverado is going to be the LTZ model, it will test this model and send the results in.

This is where it gets tricky.

Worse MPG! 2021 Chevy Silverado Duramax diesel 4wd sees big drop
This Chevy Silverado Trail Boss won’t get the same fuel economy as a base model. Why? Lift and tires. (Photo courtesy Chevy)

Most consumers know when you lift a truck and put bigger tires on it, you get worse fuel economy. It is physics. Automakers know this, too, and they often rate their off-road variants with the same fuel economy of the model they want the EPA ratings for. This makes them seem more competitive on paper with their rivals while explaining to consumers the EPA numbers are “estimates” and they shouldn’t be taken for fact.

There have been lawsuits over this as you would imagine — like the Ford Ranger one we covered a few months ago.

With more stock, off-road configured trucks coming to market, many automakers are getting a bit smarter, trying to avoid lawsuits, and are rating this trucks with a higher rating. This also applies to trucks with more bells and whistles.

So, what happened then? GM guessed consumers were going to buy the lower trim level of the Silverado with the 3.0-liter Duramax diesel engine, and instead, consumers bought a higher trim level. In order to stay EPA complaint, GM revised its numbers to reflect what consumers were buying, and the additional weight of the more options on this truck bring down the fuel economy.

Make sense?

The bottom line 

While, yes, EPA estimates are just that, estimates, they were created to give consumers guidance on what they could reasonably expect to see for fuel usage when they bought a new truck. The recent controversy over VW and Ram with its EcoDiesel has made the EPA more stringent — aka pissed off  — and automakers are paying more attention to what numbers they put on the sticker.

This is good for them and good for you, the consumer.

Related posts:

Ford F-150, Ranger mired in new fuel economy lawsuit

U.S. Justice Department Demands FCA Recall EcoDiesel, Pay Fines

Shocker! 2019 Chevy Silverado 1500 MPG vs 2018 Chevy Silverado 1500




  1. Interesting. I’m wondering if the drop in fuel economy rating is related to the substantial price drop. It would kind of make sense to lower the price if the fuel economy rating is really not as good since that is usually the reason to buy a half ton diesel.


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