2020 GMC AT4 MPG Disapointed

i82much · November 17, 2019

4 hours ago, Hydro4acid said:

In my 2020 6.2 Denali, going 75-80 I got 23-25 mpg over 500 miles. I'm pretty pleased with this truck on the highway. Power when u want, mileage when u need it.

fuelly shows about 12 for 6.0 HD trucks and 16.5 for 6.2 half tons. I would guess your average 6.2 owner sees maybe 18.5 highway.

mistaare · November 20, 2019

I have a 2020 AT4, coming from a 160,000 mile Tacoma that I had since new. It had a 2" lift, 32" MT tires a cap and a couple hundred pounds of gear full time. It had a 21 gallon tank and I would get 210 miles to a tank. I would hand calculate between 12-14 mpg.

My AT4 has almost 2000 miles. I am getting 14.5-15 mpg right now (hand calculated). I have a cap ordered and will carry a couple hundred pounds of stuff in the back. I am hoping to keep getting 15-16 mpg once everything is broken in. I keep reading that mileage keeps inproving for first several thousand miles.

I am curious to see how bad of a hit I am going to take when I add the cap.

i82much · November 22, 2019

On 11/20/2019 at 8:55 AM, mistaare said:

I have a 2020 AT4, coming from a 160,000 mile Tacoma that I had since new. It had a 2" lift, 32" MT tires a cap and a couple hundred pounds of gear full time. It had a 21 gallon tank and I would get 210 miles to a tank. I would hand calculate between 12-14 mpg.

My AT4 has almost 2000 miles. I am getting 14.5-15 mpg right now (hand calculated). I have a cap ordered and will carry a couple hundred pounds of stuff in the back. I am hoping to keep getting 15-16 mpg once everything is broken in. I keep reading that mileage keeps inproving for first several thousand miles.

I am curious to see how bad of a hit I am going to take when I add the cap.

i have a snugtop midrise with the heavy duty roof and my fuel economy is consistent with what other 6.0 HD owners report. I do not think the cap is a big deal. A lift screws up aero bad, aggressive tires create rolling resistance, but a modern cap has decent aero and probably isn’t much different than just driving around with a fat friend in the passenger seat.

19ShadowCustom · December 30, 2019

I know its not apples to apples, but my 4.3/6speed truck has the old AFM motor in it and it consistently knocked 20-21 mpg, combined. they have me in a 5.3/ 8 speed for a loaner and I'm not impressed, 15.5 mpg.... for a truck that has DFM that's supposed to be better. If I could just get my truck back.... no parts available.

mistaare · December 30, 2019

30 minutes ago, 19ShadowCustom said:

I know its not apples to apples, but my 4.3/6speed truck has the old AFM motor in it and it consistently knocked 20-21 mpg, combined. they have me in a 5.3/ 8 speed for a loaner and I'm not impressed, 15.5 mpg.... for a truck that has DFM that's supposed to be better. If I could just get my truck back.... no parts available.

I know I’m going to hear ‘you don’t buy a truck for the mpg’ but I did expect a little better out of 5.3/10 spd and I drive like a grandpa.

SquireSCA · December 30, 2019

I have never gotten the mileage that the manufacturer claims... I buy the vehicle for what I want, or need to drive. Gas economy to me is just the cost of doing business.

The 2mpg difference on paper, translates to like $3 when I fill the truck. It's negligible...

MaverickZ71 · January 8, 2020

1) Never trust the fuel mileage show in the DIC. Many of them prove to be way overoptimistic on mpg and gallons used. It has been suggested on here that GM does one DIC calibration each year for 1500s and your mileage may vary greatly from that depending on engine/transmission/rear gear/all terrain tire option/driving style.

2) The fuel mileage estimates shown on the factory window sticker have the average mpg calculated at 50mph. Around here, highway speed is 75 to 80+mph. If you drove 50mph, you'd soon be punted into the weeds. Many road tests (Car & Driver, Motor Trend, etc.) show their actual obtained highway mileage is closer to the EPA combined rating and the actual combined mileage is closer to the EPA city rating. Especially if you drive in 'severe usage' conditions or have a heavy throttle foot.

3) Winter fuel, fuel containing ethanol, and fuel of questionable quality all negatively affect fuel mileage.

Edited January 8, 2020 by MaverickZ71

mistaare · January 9, 2020

My last three fill ups have been spot on with hand calculation vs DIC.

John Grabowski · January 14, 2020

Purchased a 2020 2500HD with the 6.6 gas engine after Christmas and have about 1200 miles on it. Using a OBD scanner, I am getting roughly 13.7 real time mileage and on a straight run on the highway with cruze speed set at 80, I am getting about 15

MacLaren · January 14, 2020

Very happy with my 2019 5.3 4x4 Crew Z71

I just recently filled her up with 93. The first time with 93 actually. There is a difference imo.

So far, I'm getting 25.0 mpg and have went, I think 345 miles and shes at half a tank. Granted, I've not been breaking any speed limits, but I'm not goin so slow as to make people mad either.

Supercup · January 22, 2020

I have a 2019 AT4 Carbon Pro - have 3,800 miles on it - getting about 13-14 around town and freeway. Recently I used for a week on daily commute of 120 miles per day and got 15.8 on first tank and 15.6 on second tank. That is going 80+ for half and 45-75 for the rest - with flow of traffic here in S. Cal. from OC to San Diego.

No question dropping to 70 mph or below the mileage really improves.

About to do a Ready Lift leveling kit which will raise front another 1"-1.5" or so - so not planning on any big improvements in the future, even with more mileage.

Just wish we got a bigger fuel tank, as I would expect 10 or so with enclosed car trailer and 260 miles is not going to cut it for sure!

Edward Brady · January 23, 2020

I noticed my AT4 Carbon Pro continually sets itself into Sport mode which worsens the gas mileage. You might want to check yours to make sure you're in Comfort mode which will give you better gas mileage. Good luck.

zeon · February 1, 2020

2020 AT4 I run premium and when I can get it I run straight premium gas and average 16 in town 21 on hwy I thank it will get better when it gets broke in very happy with myAT4 I did change the tires out in the deal bought Pirelli A/T Plus been real happy with them

JD19 · February 22, 2020

I have a base 19 Sierra with the 4.3 V6. I'm only getting 14 mpg in the city and drive with a very light foot. I firmly believe the massive hood and bulkiness of the new design is creating too much wind resistance thus causing the engines to consume more fuel to punch through the air when you drive.

Ryno12 · February 22, 2020

I have a base 19 Sierra with the 4.3 V6. I'm only getting 14 mpg in the city and drive with a very light foot. I firmly believe the massive hood and bulkiness of the new design is creating too much wind resistance thus causing the engines to consume more fuel to punch through the air when you drive.

Small motors don’t necessarily equate to good gas mileage. That little engine has to work a lot harder to get that truck moving than the larger V8’s. I would think certainly a 5.3, & quite possibly even the 6.2, would get better gas mileage than your 4.3.