2021 Jeep Gladiator Diesel 3.0 horrible MPG

[caryw5150]

Can you drop some more info?
How many miles?
Do you use fuel additives?
Do you consistently fill up at the same gas station?
Do you drain the water fuel separator?

My vote is on the tsb for def consumption….
But my gut is telling me you picked up a crappy tank of fuel somewhere….
Auto Log Book https://a.co/d/2suXiQQ

Seems crazy- but if you don’t have one of these books- you should get one. Log every fill up and location. Great for logging maintenance.
Every now and then I’ll pick up a bad tank of fuel and get terrible mileage. I then black list that station. At a minimum I’ll drain the water fuel separator, if it doesn’t improve post tank I’ll change the filter.

Diesels are sensitive/finicky.

?hope things improve

awesome ideas. thanks for the info. i'll try to get a book and see what my investigation yields. i usually use 7-11 diesel however yeah i'm not a diesel aficionado.

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[caryw5150]

awesome ideas. thanks for the info. i'll try to get a book and see what my investigation yields. i usually use 7-11 diesel however yeah i'm not a diesel aficionado.

i don't use fuel additives. engine is stock. emptied the water separator. fuel mpg for my thinking is obscenely low.

 

[Escape.idiocracy]

awesome ideas. thanks for the info. i'll try to get a book and see what my investigation yields. i usually use 7-11 diesel however yeah i'm not a diesel aficionado.

If you aren’t- and I’m sure some will argue this… I run a diesel additive

Hot Shot's Secret Everyday Diesel Treatment 16 Ounce Squeeze Bottle (HSSEDT16ZS) https://a.co/d/0Y1R550

I run 1-2oz of this when I’m at the pump for a fill up.
Helps put a lubrication property back in the fuel for the fuel pump. I usually note a 1-1.5mpg increase on highway tanks.
??‍ Nothing else cheap insurance for the fuel pump


Your fuel economy is insanely low…. 18 mpg if flogging would be ok… anything lower and something is off.

Change your fuel fill up location.
Use gas buddy and see what diesel station seems to be used the most.

 

[caryw5150]

If you aren’t- and I’m sure some will argue this… I run a diesel additive

Hot Shot's Secret Everyday Diesel Treatment 16 Ounce Squeeze Bottle (HSSEDT16ZS) https://a.co/d/0Y1R550

I run 1-2oz of this when I’m at the pump for a fill up.
Helps put a lubrication property back in the fuel for the fuel pump. I usually note a 1-1.5mpg increase on highway tanks.
??‍ Nothing else cheap insurance for the fuel pump

also good to know. i'm gonna try that. yeah this low MPG has got me stumped. i need to calibrate the speedo try a tune and additive see where i end up. i mean with the tiny fuel tank which i wish there was an aftermarket fix for that also, yeah my range is greatly diminished.

 

[caryw5150]

MRTUNING

super thanks for the help.

 

[Escape.idiocracy]

also good to know. i'm gonna try that. yeah this low MPG has got me stumped. i need to calibrate the speedo try a tune and additive see where i end up. i mean with the tiny fuel tank which i wish there was an aftermarket fix for that also, yeah my range is greatly diminished.

The fuel tank is small… we usually get 400 miles per tank in town and 460/470 miles per tank on the highway.


Calibrate the Speedo- I missed a post. Guessing jumped to 37” tires?

I would still expect 350mpt in own and 390-400 on highway.

 

[caryw5150]

There is a recall affecting some diesel engines that reduced DEF fluid consumption and increased MPG. I don't remember the specifics but there is a thread on it. Definitely seems like you have an issue. I'm assuming you've calibrated for tire size.

yeah my def usage is for sure weird also. i'll see what i can do to get it checked. thanks for that.

 

[caryw5150]

If you want to check quickly download a gps based speed app on your phone and hit the interstate to see how far you are off. I use speed box.

wow... super thanks. great idea. simple however yeah i shouldve known to try this.

 

[PnwGladiatorBuild]

Im running a 2" lift and 37s, with a RTT, Awning and Canopy and I still average 20-22 mpg.

How new is your engine? Did you break it in yet? When I just got the truck my first 2k miles I was averaging lower then I started to get better mileage.

Also, after wheels and/or lift you need to re calibrate the speedo.. it might be affecting the mpg counter.

Unless you just floor it everywhere you drive... something is up with your mileage.

 

[CerOf]

Get your Speedo corrected for tire size. This also affects the transmission shift points and probably other things.

Drive it a month after you do this.

Then report back. If still terrible, take it to the dealership before doing anything else. Don’t want to void your warranty with a tune, a tune won’t fix broke.

 

[ShawnwFL]

If your speedos not corrected you are travelling further than the computer thinks, so when the computer calculates mpg based on the artificially low distance travelled value it’s going to report lower fuel mileage.

I had a buddy with the opposite issue. He had very tiny tires on his truck (was a trend back in the early 2000s) and claimed he got 75 mpg. He didn’t adjust his speedo so the vehicle thought it went further than it actually did. Same issue, different tire size.

 

[Otisday]

2021 Jeep Gladiator diesel on 37's getting 13-14mpg in city driving. wondering if there are issues anyone knows could be causing. drives fine. no issues as i know it, aside from tiny gas tank, reported fuel mpg is horrible.

I have a 2021 Dieseland my around town mileage is 22 mpg and my hwy is 25-30 mpg

 

[Jteakus]

For sure calibrate for tire size. I use a Taser plus it does so much more. Add diesel additive. I use Amsoil. Lubricity has been greatly reduced in diesel, your injectors and pump will last much longer with Your choice of quality additive. I'm on 37's. I bought some 4.10's knowing I was going up in tire size but have decided not to change from 3.73's because the diesel is just happy with them. I don't hot rod mine and I'm getting mid-20 mpg. Check with dealer to see if DEF flash has been performed. I had it done on my 2020 JL but my 2022 JT already had it flashed from factory. Keep us posted please.

 

[RS3]

22 Rubicon all stock aside from the Tazer. Of the first three tanks I checked (hand calculated) I only got 19-20 mpg being a mix of town/highway. My dash said I was averaging 22.8 but I don't necessarily take that as accurate.

 

[Randonexplosion]

Another vote for the speedo correction. I just installed my 37s and lift and have only ran through 1/2 a tank.

I installed the 37s and lift over the weekend before my tazer showed up. A few days of driving dropped my avg MPG from over 20 to 17. First day with the tazer today and its already coming back up over 18 and climbing. Im interested to see what it levels off at. I never got the 25-30 that some guys are claiming but im at 6200' and drive mostly around town.

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