2021 Gladiator Rubicon MPG

[Dannymums]

Hey everyone,

thanks for accepting me to the forum. So this is my first experience with having a jeep or any off road capable vehicle. Im starting to think there is something wrong and i wanted to reach out to anyone that may be going through the same MPG issues or just to find out what i should be expecting. I own a 2021 Jeep Gladiator Rubicon. I purchased with 4200 miles so it was practically brand new. What i dont know if what mods were done to it with first owner besides the obvious (rims/tires). I took it to mechanic who specializes in lift kits and is Jeep certified (for warranty) and he stated that i have the 2” Mopar lift. It came with 20x10 Fuel wheels wrapped in Nitto Trail grapplers 35x12.5R20. I added the RC 50” lightbar, Rugged Ridge window Deflectors, and Tailgate “GLADIATOR” Badge, but no mods have been done by me that would affect my MPG except maybe weight which is miniscule. I drive mostly highway miles and my AVG mpg is steady at around 10-11. I know with having 35” tires and 20” wheels, my mpg would drop but not this much. Can anyone recommend a solution or at least tell me what i should be at mpg wise? Thought about switching to the Nitto Ridge Grapplers but would that even increase my mpg? Any advice would be appreciated.

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[USMC-SSGT]

Edit to add: your truck has essentially everything on the list that crushes MPG. Lift heavy tires larger tires heavy wheels offset wheels stubby front bumper Huge light bar Rack mount tent n??

I have a similar setup as yours and average 15.5 (although I’ve been regeared to 4.88.) The gears wouldn’t make that much of a difference.

Steps:
1: verify your speedometer has been adjusted for the larger tires. Can use something simple like a gps speed app to compare

2: drive like an old immigrant lady on an expired visa. Don’t exceed 70 on the highway either max. Driving habits alone can take you from 12-16 without much work at all. I drive pretty conservatively and can hit 16 on a tank, but average is still 15.5. If I “got after it” and did 75+ on the freeway I’m lucky to see 12.

 

[ZoMojave]

Edit to add: your truck has essentially everything on the list that crushes MPG. Lift heavy tires larger tires heavy wheels offset wheels stubby front bumper Huge light bar Rack mount tent n??

I have a similar setup as yours and average 15.5 (although I’ve been regeared to 4.88.) The gears wouldn’t make that much of a difference.

Steps:
1: verify your speedometer has been adjusted for the larger tires. Can use something simple like a gps speed app to compare

2: drive like an old immigrant lady on an expired visa. Don’t exceed 70 on the highway either max. Driving habits alone can take you from 12-16 without much work at all. I drive pretty conservatively and can hit 16 on a tank, but average is still 15.5. If I “got after it” and did 75+ on the freeway I’m lucky to see 12.

Welcome to the forum. I must agree (what has been already stated) the mileage has been killed by the changes made to the truck. Not that they get great MPG anyway. My bone stock 2022 Mojo gets 16 mpg. Still breaking it in but doubt it will increase much.

And I drive like an old lady born in the U.S.A.

 

[ArmyMP]

Diesel

 

[NachoRuby]

My only mod is the 35" tires, and mine is a 6 speed, but that still sounds very low. I get 16.5 city, 21 highway, 18.5 overall. I got like 1 mpg better on the stock tires. I'd first check to make sure that your speedometer has been recalibrated.

 

[Firesmith102]

You need to install a tazer or other device to update your computer on tire size. I am running 37s on a 3.5 inch lift and average 16.5.

 

[XJFanatic]

Echo what everyone else is saying your computer is not corrected. I am getting 17-18 in town and 19-20 on the highway with my max tow and 35s.

One thing often not discussed is the 7 and 8.4” radio equipped JL/JT GPS correct the actual speedo, the odometer does not adjust based on GPS. I only discovered this after researching my phenomena after adjusting tire size, noticing everything was off 3-4 mph, checking again a few days later and it was perfect.

I will see if I can find the thread over on the JL forum. Here is the specific post explaining it.

https://www.jlwranglerforums.com/fo...nd-8-speed-shifting-issues.63503/post-1848081

 

[chorky]

Agree with others that you probably need to reprogram according to tire size.

That being said - one thing I see hardly ever mentioned in these questions is where people live. There's a huge difference between me living in the rockies where I could have a 6,000 foot elevation change in a couple hours time with highway posted speeds of 80 as compared to somebody else living in the south who may only see 500 feet of elevation change throughout 10 years with highway speeds of 60. So lots of variables there.

In the rockies, with just under 500 miles on the clock of a stock Rubi - I am currently averaging 18.2 highway keeping speeds 65-75.

Diesel

Your making me jealous and wish I had gotten the diesel...

 

[Papa mojo]

It does sound unreasonably low. I live in the Appalachian mountains and while they are not the Rockies some grades are pretty steep. My Mojave (stock) has 2500 miles and I get from 17.8 to 19 mpg depending where I am at the time. One thing that seems to help is using the cruise as much as possible. I tried 93 once and was getting 20.3 but can't afford much of that.

 

[JD101]

Stock mine was at like 19.2 over 2200 mile road trip
37x12.50 STT Pro , 4.10 . 15.5 -16
37s 5.13 . 16-17
38x13.50 Trail Grap 5.13. 12.7-14

Now I have stubby bumper with non recessed winch , pod lights , and fender chop . Basically a parachute . I'm at low elevation and all were during winter ( Michigan ) temps and fuel .I am tazer corrected . Something doesn't add up with your fuel economy. Start by using a good gps to check your speed at 70mph against the speedo.

 

[JD101]

I would be astonished if the recal is the only issue . You would know if the speedo was reading that far off. Also do a hand calc on your next fill up . You will need to drive a know distance tho , or log miles on a separate GPS.

 

[DCPHOENIX]

That’s really low. Has to be something else going on surely?

Agree with the post about differences in elevation though.
Phoenix - Flagstaff and averaged 18mpg at 65mph to 70mph. Elevation gain is around 6000ft
Phoenix - Tucson averaged 24.5mpg at 70mph. Elevation gain roughly 1000ft.

 

[Dannymums]

Stock mine was at like 19.2 over 2200 mile road trip
37x12.50 STT Pro , 4.10 . 15.5 -16
37s 5.13 . 16-17
38x13.50 Trail Grap 5.13. 12.7-14

Now I have stubby bumper with non recessed winch , pod lights , and fender chop . Basically a parachute . I'm at low elevation and all were during winter ( Michigan ) temps and fuel .I am tazer corrected . Something doesn't add up with your fuel economy. Start by using a good gps to check your speed at 70mph against the speedo.

I use waze on my phone and just finished a 50 mile run to the Jersey Shore and gps stated 72 and speedo was at 68. Should i purchase a Tazer?

 

[NachoRuby]

I use waze on my phone and just finished a 50 mile run to the Jersey Shore and gps stated 72 and speedo was at 68. Should i purchase a Tazer?

If all you plan on doing is change the tire size, I'd get a jscan, or even get the dealership to do it. The dealership did mine for $125. I have a tazer too though. It does other stuff.

 

[chorky]

I use waze on my phone and just finished a 50 mile run to the Jersey Shore and gps stated 72 and speedo was at 68. Should i purchase a Tazer?

4 mies difference? that's not enough to be causing the fuel mileage concern you have.

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