2022 AT4 with 3.0 diesel gas mileage swing ratings?

Klutch · March 9, 2022

If you're reading this for the first time and have a 1500 AT4 w/3.0 can you reply with the gas mileage shown on your window sticker?

Ordered a 22 AT4 with the 3.0 I6 but noticed the window stickers on 'in transit' trucks via GMC's site that the gas mileage ratings vary wildly. I first noticed it with the SLT/Denali-vs AT4 with the exact drivetrain (engine, trans, drive, rear end). Then I started looking at just AT4's themselves and they vary. Some have a combined rating of 24 and others are 21.....

Here is an example of a 24 https://cws.gm.com/vs-cws/vehshop/v2/vehicle/windowsticker?vin=3GTUUEET2NG502131&bac=116384

Here is an example of a 21 https://cws.gm.com/vs-cws/vehshop/v2/vehicle/windowsticker?vin=3GTUUEET3NG502011&bac=118330

Here are some SLT's that are consistently 24

https://cws.gm.com/vs-cws/vehshop/v2/vehicle/windowsticker?vin=3GTUUDET4NG502013&bac=116211

https://cws.gm.com/vs-cws/vehshop/v2/vehicle/windowsticker?vin=3GTUUDET7NG501597&bac=286367

What am I missing??? I've found far fewer AT4's that vary, nearly every one of them is the 21 combined. Even if they all were rated at 21 why would the gas mileage be so different from the SLT/Denali's? I get there is a little more weight to them maybe but that's a pretty giant difference

I'm not trying to turn this into a "it's a truck, who cares" debate. Trying to understand the differences

Edited March 10, 2022 by Klutch

f8l vnm · March 9, 2022

Could it be the 18s vs 20s?

DemonWorks · March 9, 2022

3.73's vs 3.23's ? Rear gear

latreille89 · March 9, 2022

2" factory lift, rims/tires, gearing... all of those will change the mileage ratings.

Klutch · March 10, 2022

2 hours ago, f8l vnm said:

Could it be the 18s vs 20s?

Starting to wonder if it's a mistake of some sort. As provided, I've found at least 1 window sticker that is the 24 but even the GMC site for the overview says the same thing, see attachment. For those that mention axle ratios, wheels, tires, lift. I mentioned the powertrains were identical. The wheels/tires might be but 3mpg on a difference is a huge difference. I'm going to dig into the Chevy site to see what the TB is in comparison.

Klutch · March 10, 2022

Can anyone with a current body AT4 w/3.0 and 3.23 gears confirm what their window sticker says?

Looking at the 22 LTD's I've found both window stickers and with various Chevy's as well. If you haven't tried to build a AT4, there really aren't any options for them as far as axle ratios or engine combos. It's 3.0* or 6.2 and 3.23* or 3.73

Klutch · March 10, 2022

Figured it out. If you get the 18" wheels they come with MT tires and no other options. If you get the 20's w/AT tires that's the smoking gun. Can't believe there is that big of a change in mileage. Could swore I'd found some with the higher rating w/18's but apparently not.

f8l vnm · March 10, 2022

275/65/18 vs 275/60/20... one is almost a 33 tire while the other one is 32 inch tire. still crazy difference. Maybe this is why GM didn't put something bigger then 33s on the new ZR2 . ( MPG standards ?)

MTU Alum · March 11, 2022

The rolling resistance on the duratracs is really high. The rolling resistance is almost 40% higher than the 20" tire. The lift on the AT4 also hurts aero performance.

There has been changes on how GM can report fuel economy for CAFE. GM could use to group any model within 10% of the label. Now I believe it is 7%. CAFE is really compliated on which models can shield other models.

With the chip shortages, there are items being removed that help FE. Not all of these apply to LM2 though.

#iworkforGM

Klutch · March 11, 2022

2 hours ago, MTU Alum said:

The rolling resistance on the duratracs is really high. The rolling resistance is almost 40% higher than the 20" tire. The lift on the AT4 also hurts aero performance.

There has been changes on how GM can report fuel economy for CAFE. GM could use to group any model within 10% of the label. Now I believe it is 7%. CAFE is really compliated on which models can shield other models.

With the chip shortages, there are items being removed that help FE. Not all of these apply to LM2 though.

#iworkforGM

Yeah, clearly the tires are huge factor. I changed my order to the 20's with the AT option. I just hope it comes with the Bridgestones that were on my '21. The lift doesn't seem to make a difference, the AT4 with AT tires is rated the exact same as the Denali and SLT with identical drivetrains but could fall within that grouping you spoke of. I don't see why the lift would make a difference unless it severely altered the aerodynamics

Jrodpic · March 11, 2022

Interesting find because check this out. Was eyeing a diesel Trail Boss with 20” rims and the window sticker shows the same mileage as the 18” with Duratracs. The 20” lists Goodyear Wrangler Territory tires. Apparently mud tires that kill the MPGs just as much as the Duratracs. So my question is what are the running on the 20” AT4s??

Edited March 11, 2022 by Jrodpic

Jrodpic · March 11, 2022

Forgot the sticker. Here it is:

https://www.cummingchevy.com/dealer-inspire-inventory/window-stickers/gm?vin=1GCUYFET1NZ111272

Klutch · March 11, 2022

3 minutes ago, Jrodpic said:

Interesting find because check this out. Was eyeing a diesel Trail Boss with 20” rims and the window sticker shows the same mileage as the 18” with Duratracs. The 20” lists Goodyear Wrangler Territory tires. Apparently mud tires that kill the MPGs just as much as the Duratracs. So my question is what are the running on the 20” AT4s??

The magic is the AT vs MT tires. On the AT4 the standard 18's only come with MT tires. The 20's default to MT's but have a AT option

Jrodpic · March 11, 2022

2 minutes ago, Klutch said:

The magic is the AT vs MT tires. On the AT4 the standard 18's only come with MT tires. The 20's default to MT's but have a AT option

What AT are they running on them? We are most likely picking up a diesel Boss and if I can pick up that kind of mileage with AT tires I’m switching over at the first replacement.