What kind of Gas Mileage, is normal?

Realism

Original poster
Member
Nov 25, 2015
217
Idaho
What kind of gas mileage is considered normal for our trucks.
I have a 2020 GMC Sierra 1500 SLT 5.3L V8 10 speed
I know the V8 does do more gas and I dont expect it to pull 19 mpg in town. But I have been averaging like 12-13 mpg. Yes most of my driving is in town with like 15 miles a few times a week on the freeway.
For a Truck that was touted as 22 highway 16 in town and 19 average. I feel very let down by what I am getting in mpg.
I dont haul large loads, I have All terrain tires and not the all seasons I usually got for my envoy, but I wouldnt think that would hit the fuel cost that much.
Im also very easy and grandpa ish when it comes to driving, so no hard take offs or anything foolish.

Is there something I am missing? This just feels like the trucks of the 90s where 10-12 mpg was average for a work truck.
 

Mooseman

Moderator
Dec 4, 2011
26,174
Ottawa, ON
Is this calculated or from the on-board computer? Sometimes they can be off but usually not by much.

Are the start/stop and AFM operational? Although they don't affect MPG that much, it could be something that's contributing. Other than that, check the usual suspects like an intake or vacuum leak, air filter, dirty MAF, lazy O2 sensors.
 

Mooseman

Moderator
Dec 4, 2011
26,174
Ottawa, ON
You sure you have the 10 speed and not the 8 speed? IIRC, it was only available with the LM2 diesel until 2022. Try shifting manually until you get to the highest gear.
 

Realism

Original poster
Member
Nov 25, 2015
217
Idaho
Is this calculated or from the on-board computer? Sometimes they can be off but usually not by much.

Are the start/stop and AFM operational? Although they don't affect MPG that much, it could be something that's contributing. Other than that, check the usual suspects like an intake or vacuum leak, air filter, dirty MAF, lazy O2 sensors.
Start stop functions, though I prefer to have it off. I run the AC right now so it doesnt shut off anyways. AFM, I have no clue how to check that. Intake seems good. No leaks that I can hear or detect just casually.. Air filter is clean, MAF, didnt check that, but doubt it. Havent checked O2 sensors on my scanner at all, doubt there would be anything wrong with it.
The vehicle is a certified one, so dealership went over it with a fine tooth comb before selling it.

Pretty sure it is a 10 speed. The Manufacturer sheet was in it and the vin matches up, and the sheet lists it as a 10 speed. Plus the shifting is super smooth, Cant even tell really, unlike a 6 and 8.
I will try a manual shift at some time tomorrow.

Also its from looking at the DIC, I will hand calculate it out next fill up, but it seems about right with cursory maths. Im filling up about every 4-5 days instead of my customary once a week or week and a half with my envoy. and that had a smaller tank and got better mileage.
 

Mooseman

Moderator
Dec 4, 2011
26,174
Ottawa, ON
I asked about start/stop and AFM in case they had been tuned out. On the MPG page of the DIC, it should say how many cylinders it's running on. May also help to keep it on the instant MPG page so you can monitor your driving habits and can see what your average is doing.
 

Realism

Original poster
Member
Nov 25, 2015
217
Idaho
So after a long period of time for major averages and without running the AC, it appears the fuel usage has not changed. in 2hi, I am still averaging 13-14mpg, 11-12 in city with about 16-17 on free way.

Has there been any recalls or any tsbs released related to fuel mileage? Is there a class action talked about, cuz this seems to be very much a problem if they are releasing vehicles that say you get one number but then you end up getting almost half that.
I would have gone with an older Tundra if I had known the mpg were going to be this bad. GM beat out Toyota because it was supposed to get better gas mileage.
 

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