Bad fuel mileage on 2026 1500 5.7 hemi. Highway driving

[olyelr]

2026 hemi with 3.92 gears, stock tires.

In 8th gear its about 2000 rpm at 70, and about 2200 at 80.

 

[Kwilson]

That’s pretty much where I’m sitting but window sticker shows 3.21 gear! Now I’m wondering if there was a mistake made here at the factory!!??

 

[mikeru]

That’s pretty much where I’m sitting but window sticker shows 3.21 gear! Now I’m wondering if there was a mistake made here at the factory!!??

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[Big_Bill]

On my'22 1500 Bighorn there's an option to show the gear you're in on the dash. Look in the owner's manual or just browse the options to find it..

 

[olyelr]

On my'22 1500 Bighorn there's an option to show the gear you're in on the dash. Look in the owner's manual or just browse the options to find it..

Yea the ‘26s have it too, somewhere in the settings. Puts a little number next to the D for what gear you are in.

 

[olyelr]

That’s pretty much where I’m sitting but window sticker shows 3.21 gear! Now I’m wondering if there was a mistake made here at the factory!!??

Welp, if they screwed the back up, lets hope they screwed the front up too . Have you put it in 4wd?

 

[RamDiver]

That’s pretty much where I’m sitting but window sticker shows 3.21 gear! Now I’m wondering if there was a mistake made here at the factory!!??

The rpm calculator I posted earlier is quite accurate if the correct values are entered.

Pick a speed, set the cruise and figure out the displayed rpm.

Plug in all the numbers and tweak the final ratio until the rpm matches with all the known values.

.

 

[Wild one]

That’s pretty much where I’m sitting but window sticker shows 3.21 gear! Now I’m wondering if there was a mistake made here at the factory!!??

Bottom side the drivers side rear axle tube should have a sticker with the diffs part number and in smaller numbers it should also have the gear ratio printed on it.

 

[DanAR]

2026 hemi with 3.92 gears, stock tires.

In 8th gear its about 2000 rpm at 70, and about 2200 at 80.

View attachment 582454

View attachment 582455

Mine reads exactly the same with 3.92 gears - 2000 rpm’s at 70mph. Even if the factory slipped 3.92 gears into the OP’s truck by mistake it wouldn’t be taching as high as he is reporting - unless he has some undersized tires on it.

 

[Kwilson]

Truck is bone stock!

 

[Nashveygus]

My '21 5.7 3.21 Laramie 4x4 with 35k miles is averaging 16.9 mpg city and 20.5 mpg hwy. Hwy driving between 75-80 mph. Keep tires at 37/38 lbs.

 

[airrecon]

Try keeping the speeds at 70 MPH and don't say you can't I have drove in TX so know it can be done so long as your not in the left lane.....

Driving at 75 to 80 should not reduce fuel consumption that much. I live in the SW and always drive 80 on the interstates, and barring headwinds and mountains, get 18mpg

 

[Dusty]

Truck is bone stock!

As others have pointed out, 2300 RPM at that speed doesn't match the axle ratio you think you have unless the transmission is not going into the top gear for some reason.

That aside, you are not the first in this forum to have a similar experience going from one 5.7 Hemi with many miles on it, to a fresh motor on a newer truck. Most will tell you these are long break-in motors.

My suggestion is apply a little patience and see what you get after a few thousand miles.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, 18” wheels. Build Date: 3 June 2018. Now at 149573 miles.

 

[Panduh]

My 2016 hemi with 3:92 gets 20+ mpg at 70 mph.

 

[Kwilson]

Thanks for all the feedback. I will see what happens with some more miles on this thing. It has begun to improve so I hoping for full break in!

 

[olyelr]

Out of curiosity, crawl under the rear axle and see what your data tag shows for gearing.




If it is indeed 3.21 (and the actual gearing is) and you are having those rpm’s at those speeds, your torque converter must be slipping.

 

[Kwilson]

I will look thanks

 

[olyelr]

Welp, burned up a full tank of gas driving my normal routes (northern mi 55mph roads, minimal traffic lights, some hills, no mountains etc.), but drove like grandma going to church the entire time. It was terrible lol!

Mustered out 18.4 mpg (hand calculated, the dash showed 19). 2026 hemi, 3.92 gears with off road package. All stock. 10,600 miles.





Im not sure how i could possibly get any better than that with this truck. Not ******** about it, but the ‘17 without etorque (3.21 gears) i had did better.

 

[Kwilson]

Well mines getting better driving like grandma avg 16 right now but still under 5K miles

 

[Bunk22]

My 2023 Ram 5.7 with e-Torque and 3.21 gears got poor gas mileage. It did best with 89 octane but best I saw was 19 MPG on the highway, at 65 mph. If I cruised at 75, I would get 17-18 MPG. Combined, my average was 13-14 on 89 octane. On top of that, I purchased a Ram truck with the smallest gas tank, 23 gallons. My new 26 Ram 1500 Warlock with the Hurricane and 3.92 gears does much better, along with a larger 26 gallon tank.