Poor gas mileage

[theblet]

Idling and remote starting def hurt my avg mpg. I also notice when taking off from a dead stop, accelerating slowly the instant is 1 to 3. If I take off quicker it’s still the same, but takes less time to get to speed. Then I set the cruise if I can.

my avg is at 18.9 right now with mixed driving. If I hadn’t left the truck running for 29 min at the car wash it would prob be closer to 20 mpg

 

[CogitoErgoLevo]

I only have 1000 miles on the truck but i am getting 17-17.5 mpg so far. 70% highway / 30% city.

 

[ColoradoCub]

Yup, the MPGs are terrible with this truck.
That being said, I didn’t buy it because of great MPG.......but 16 mpg would be nice.

You are running 35” tires on a lifted Ram and complaining about fuel mileage?

 

[ColoradoCub]

I think 3.92’s with the little tires these trucks come with is a big part of the problem. I would bet by switching to a slightly taller tire (in the same load class) would yield better fuel mileage. It would effectively change the gearing to a more fuel mileage happy ratio. I could easily get 19-20 on a long trip with my 2019 Big Horn CC 4x4 running lightweight 275/65/20 tires (which are 34” tall) compared to the 32” tires it came with. But with that said I’m running 10 ply 33” tires on my current 2020 Laramie and I always average 17” ish mixed driving when I fuel up. I can get 19+ on highway trips pretty regularly. It’s hard for me to get a good highway mileage test on any flat land living in the mountains, my drives are 50/50 uphill downhill no matter where I go. I don’t do much city driving at all.

 

[Buz]

I think 3.92’s with the little tires these trucks come with is a big part of the problem. I would bet by switching to a slightly taller tire (in the same load class) would yield better fuel mileage. It would effectively change the gearing to a more fuel mileage happy ratio.

I just did this very thing. Went up one size to 275/60/20 which changes the 3.92 rear to 3.79. Tires are same metric category as stock Bridgestone's. (no XL or D or E load rating).
Hopefully I'll see a slight uptick in my abysmal 12MPG I'm currently getting with 80% around town/short trips. But I think most of my problem is the short trips. I think the Hemi is extra thirsty when it's not up to temperature.

FYI, going to a 275/65/20 changes the 3.92 rear to 3.67, but now you're getting into a much heavier tire and harsher ride.

 

[brian42]

I think 3.92’s with the little tires these trucks come with is a big part of the problem. I would bet by switching to a slightly taller tire (in the same load class) would yield better fuel mileage. It would effectively change the gearing to a more fuel mileage happy ratio.

You will have a bit of an offset due to the wider contact patch and heavier tire. These all lead to increased friction and will take more energy to move the truck (the heavier tire is all rotational inertia).

 

[MN*Ram*1500]

I just picked up my 2021 2500 Laramie diesel 4X4 on 22 FEB 21, only about two and a half weeks ago. I have only filled it up twice in the 748 miles I have driven it so far so this is an extremely small sample size.

My combined city and highway, with a lot of idling because of the below zero temps here in Minnesota, right now is 15.36 mpg.

 

[ColoradoCub]

You will have a bit of an offset due to the wider contact patch and heavier tire. These all lead to increased friction and will take more energy to move the truck (the heavier tire is all rotational inertia).

Not always, an increase from a factory 31.9” tire like the 275/55/20 that rams come with to a 275/60/20 33” tire has the same contact patch, weighs nearly the same and is just over an 1” taller. I believe this would improve the fuel mileage on stock rams just by changing the final gear ratio. Now if a guy gets into taller and wider and especially LT rated tires then it’s most likely going to hurt mileage, especially when a guy goes from a 45-50 lb stock tire to a 70+ lb LT tire, that increased rolling resistance is unavoidable.

 

[brian42]

That's why I was very careful on my tire selection. I kept the same size (I have no intention of going larger which is why I was fine with the 3.21 rear) and actually dropped a couple of pounds per tire with my XL-rated Ridge Grapplers.

My last truck was an older Ford F-250 4x4 diesel that didn't really care what I did to it. 600+ lb-ft of torque @ 1600 RPM overcomes a lot of stuff (including kids toys you don't see in the driveway when you back up ). With this truck, though, I'm very careful on what I do to it.

Even with the same weight the taller tire will have a longer radius and, as negligible it might be, it is easier to swing a shorter golf club than a longer one.

 

[theblet]

I think 3.92’s with the little tires these trucks come with is a big part of the problem. I would bet by switching to a slightly taller tire (in the same load class) would yield better fuel mileage. It would effectively change the gearing to a more fuel mileage happy ratio. I could easily get 19-20 on a long trip with my 2019 Big Horn CC 4x4 running lightweight 275/65/20 tires (which are 34” tall) compared to the 32” tires it came with. But with that said I’m running 10 ply 33” tires on my current 2020 Laramie and I always average 17” ish mixed driving when I fuel up. I can get 19+ on highway trips pretty regularly. It’s hard for me to get a good highway mileage test on any flat land living in the mountains, my drives are 50/50 uphill downhill no matter where I go. I don’t do much city driving at all.

Ive always been told the opposite. How would that affect my bighorn with the 3.21 rear end if I run 275/60r20?

 

[theblet]

I just did this very thing. Went up one size to 275/60/20 which changes the 3.92 rear to 3.79. Tires are same metric category as stock Bridgestone's. (no XL or D or E load rating).
Hopefully I'll see a slight uptick in my abysmal 12MPG I'm currently getting with 80% around town/short trips. But I think most of my problem is the short trips. I think the Hemi is extra thirsty when it's not up to temperature.

FYI, going to a 275/65/20 changes the 3.92 rear to 3.67, but now you're getting into a much heavier tire and harsher ride.

Curious to see how this turns out. Please let us know.

 

[ColoradoCub]

Ive always been told the opposite. How would that affect my bighorn with the 3.21 rear end if I run 275/60r20?

It would effectively do the same thing it does to the 3.92 equipped trucks, lower your final gear ratio, which I think would further rob power from your truck. The 3.21’s usually get better mileage than the 3.92’s simply because they run lower RPMS at highway speeds. When I had my bighorn going from the factory tires to the 275/65/20’s reduced my highway rpms by like 200 RPMS.

 

[Willwork4truck]

Yea it would not be a great idea to drop 3.21's down much more at all...Maybe if in flatlands or something.

 

[theblet]

Wow really. I don’t tow anything so maybe it wouldn’t be a big deal. Don’t want to make it run in 7th gear tho. Not sure what to do

 

[Usa450r]

You are running 35” tires on a lifted Ram and complaining about fuel mileage?

Did you read my post? I said I didn’t buy the ram because of mpg. I simply said 16 would be nice. Swipe right.....

 

[Buz]

Ive always been told the opposite. How would that affect my bighorn with the 3.21 rear end if I run 275/60r20?

275/60R20's will drop your 3.21 rear to 3.10.
I honestly would think twice about doing it. Your engine may begin to 'lug' more often. You're already at the bottom end of gearing, which is great for MPG, but I think it's maxed out at 3.21.

 

[theblet]

I gotcha. It also seems that 275/60r20's are much more expensive that the stock size. i would rather go a little wider.

 

[John89]

Im averaging about 18.9 MPG with a mixture of 70% Highway/30% City. I have the eTorque version with about 600-ish miles on it currently. However when I first got the truck it was at 14.9 MPG, and it could be attributed to my driving style. I’ve found that accelerating “normally” to get up to speed without worrying about gas and then letting go of the pedal and lightly pressing it again to maintain your speed works and increases your average MPG. That’s the only picture I have which is a bit outdated (Im currently @ 18.9 mpg) but I’d say that’s near what should be expected out of a 5.7L hemi with occasional semi-aggressive acceleration.

 

[theblet]

When I first bought my truck I was making 14 because I would start it and sit in it to learn all the features/settings.

 

[IvoryHemi]

275/60R20's will drop your 3.21 rear to 3.10.
I honestly would think twice about doing it. Your engine may begin to 'lug' more often. You're already at the bottom end of gearing, which is great for MPG, but I think it's maxed out at 3.21.

I don’t think it would be so bad.

The 5.7L/ 8HP70 Durango has 265/50/20 and 3.09 gears. Even with its 5,400 lb curb weight there is plenty of power and never lugged. I was able to pull 22-24 mpg highway.