Does Jeep purposely design their vehicles to get 19 mpg?

[Afternoon Spray]

Even cruise control at 64 MPH, letting the computer handle the throttle on completely flat pavement I get this.

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[Over The Hill]

I have 3 and mileage varies from 16 to 23
2001 TJ , 4" lift 12.50 33r15 @16
2012 JGC Overland 3.6l with 5 speed auto @23+
2021 JT gladiator 3.6l with 8 speed auto @19+
All different, but AVERAGE of - - - 19 MPG

 

[Master_Cylinder]

My first car was a 1969 Pontiac Catalina with a 400 V8. It got 8 MPG. As long as I get more than that, I’ll be happy.

 

[Dilly’S Willy]

I get 18-20 average on 37s and heavy. I get 15ish towing my camper. At times I wish I was getting better, but then I remember what I'd be getting in the same conditions with a gasser and then I don't feel so bad.

I have often wondered why, with todays tech our vehicles (in general) still get such shit fuel economy. I'm sure part is due to regulations, part is due to greedy oil companies having too much influence.

Wait until you find out why modern engines since EFI blow up when stock vs modded correctly...EPA regulations.
- "Yeah, I KNOW this tuning is bad for the engine, but it's great for emissions with the devices we make everyone use to reduce said emissions. What? No I KNOW running AFRs 18:1 IN BOOST is dangerous. Yes, I'm aware running 38* of timing isn't making usable torque, but look at how little CO/NOx we create! Huh? Oh, no, forcing the throttle plate to stay open after you lift off the throttle and the engine keeps revving longer than you want/need? They will just need to learn to drive how we want them to."

They literally couldn't care less about making reliable engines, only about their lobbyists. Remember Cash for Clunkers? Pepperidge Farms remembers...

Crying in my 14.5-15.2 MPG I get with my manual transmission Rubicon on 33" KO2s. But also not crying because doors off season is upon us.

Slacker, had the doors off a week ago and it was only 54*

Even cruise control at 64 MPH, letting the computer handle the throttle on completely flat pavement I get this.

I'm going to guess you have 3.73 (final drive ratio/Ring-Pinion) paired with your manual transmission?

I learned that if not going AT LEAST 65mph, don't use 5th and stay in 4th, especially with cruise.
Same for 6th, if you're not driving AT LEAST 75mph, 6th is pointless the moment you need to speed up or maintain speed on an incline, it's a true OD gear, so is 5th. That's why I call these manuals a "4 speed with double OverDrive".

FYI I drove 20k miles between August 2025 and yesterday, so I've spent more time than most learning the quirks of MPGs and throttle response. 27k to 49k in that time. 87oct to 93oct, and I found 93 doesn't give any more power or mpg, MAYBE slightly less rough idle, but not always either. You need to be tuned for 93oct to matter. Just don't use 85/86oct with higher E (Ethanol) rating unless tuned for it, they're pushing E15 currently across the country.

I don't baby my JTW, but I drive it like a diesel should be. Normal driving, and occasional redline pulls to clear everything out. Still getting 18+mpg.

 

[Wageslave]

Even cruise control at 64 MPH, letting the computer handle the throttle on completely flat pavement I get this.

At least with the automatics, cruise control is a little too ambitious for my driving style. It loves to downshift at the slightest inconvenience and will occasionally drop all the way into 6th when it hits a hill, even when I have no problems holding speed in 8th gear with the pedal.

 

[Dilly’S Willy]

At least with the automatics, cruise control is a little too ambitious for my driving style. It loves to downshift at the slightest inconvenience and will occasionally drop all the way into 6th when it hits a hill, even when I have no problems holding speed in 8th gear with the pedal.

Try using manual mode and going up that hill in 6th without allowing it to shift, it will take longer. 10mpg for 3 seconds is still better than 10mpg for 15 seconds. Autos are programmed to keep your engine in its "efficient" range based on requested input. You wouldn't want to lug the engine at 1800rpm up a hill in a high gear (6/7/8th for autos, 5/6th for manuals).

 

[Janster]

Not all Jeeps get bad mileage.

. Wait for it….wait for it……. There’s these ghostly gremlins that suck all the gas out while you’re in bed sleeping. The next morning - you’ll be bck down to 13mpg.

 

[Wageslave]

Try using manual mode and going up that hill in 6th without allowing it to shift, it will take longer. 10mpg for 3 seconds is still better than 10mpg for 15 seconds. Autos are programmed to keep your engine in its "efficient" range based on requested input. You wouldn't want to lug the engine at 1800rpm up a hill in a high gear (6/7/8th for autos, 5/6th for manuals).

My problem is when it downshifts over and over and over again on a grade where it shouldn't have to at all. If I am going up one long but gradual grade, the transmission shouldn't shift from 8-7-8-6-7-8-7-8-6-7-8 when I have no problems holding speed in 8th when it is off. If I was truly lugging the engine, the transmission should downshift when I am running the pedal. The cruise control is just commanding more throttle than it needs to get up to speed faster. It may be more efficient to do that but I definitely don't want to listen to the transmission shift over and over again.

 

[JonMN]

My stock 2024 Mojave has a long term average of 16.9. Drops a lot if I am hitting 75 on the freeway. No complaints, however. Funny, the car I traded for the Jeep had a V8 with 455 HP, and averaged about 22 MPG. I guess aerodynamics matter . . .

 

[Afternoon Spray]

I'm going to guess you have 3.73 (final drive ratio/Ring-Pinion) paired with your manual transmission?

I learned that if not going AT LEAST 65mph, don't use 5th and stay in 4th, especially with cruise.
Same for 6th, if you're not driving AT LEAST 75mph, 6th is pointless the moment you need to speed up or maintain speed on an incline, it's a true OD gear, so is 5th. That's why I call these manuals a "4 speed with double OverDrive".

I actually have the 4.10s with the manual transmission. It's a Rubicon.

 

[MeanGreen]

Anyone take the time to figured out their real world MPG? I did it the first time last week on my Gladiator and I averaged 17.68mpg vs the 16 mpg my display said. I plan on doing it for the next couple fill ups to see what that average is. I've on this on other vehicles in the past and it was closer.

 

[moparnut72]

I remember driving my Godfather's Dodge Charger 440 Magnum. I punched the accelerator and could visibly watch the gas needle move in the bad direction

I had a 440 Magnum out of a wrecked Charger. I put the whole drivetrain in a 1954 Dodge pickup. It sat up high and the last two cylinders in the cab, not much room under the hood. It was kind of a 60's altered. Even though I carried quite a bit of construction equipment in the truck I still got 18+ mpg. I kept my foot out of it and let that 375 HP motor loaf along. But if I wanted to nail it all bets were off.
Edit: I have less than 1,000 miles on my Gladiator but I am averaging low 20's. Not the first Pentastar we have owned, one of our Durangos would get 27 on the highway.
kk

 

[WambliSka]

In all fairness it's impossible to nail what a standard MPG number looks like for Gladiators, especially lacking details, because the variables in tire sizes, gearing, suspension, driving habits, optional equipment ike lights, racks, overland tents etc is infinite. When I got my Overland with street LT tires I was getting 20s. Then I added lights and lost a mile or two. When I switched to 34' AT's the mileage went down to the high teens and when I added the leveling kit it went to mid teens around town and 17-18 highway and 8th gear was just a wish, even on flats. So even with the same car and same driver it was a changing evolutionary game.

In summary, trying to look at just numbers without knowing if they come from a guy driving like grandma on 31" thin LT tires vs some dude running a Sport with a 4" lift and 37" Mts gunning from one light to another is kind'a useless.

 

[Dilly’S Willy]

My problem is when it downshifts over and over and over again on a grade where it shouldn't have to at all. If I am going up one long but gradual grade, the transmission shouldn't shift from 8-7-8-6-7-8-7-8-6-7-8 when I have no problems holding speed in 8th when it is off. If I was truly lugging the engine, the transmission should downshift when I am running the pedal. The cruise control is just commanding more throttle than it needs to get up to speed faster. It may be more efficient to do that but I definitely don't want to listen to the transmission shift over and over again.

Assuming stock tire size?

You have a diesel first of all, so you're already making 2-3x the usable torque us gassers are, and a lower RPM redline. Second, you COULD use manual mode in the hills and not have the "issue" you talk about with gear hunting in hills. OR just let the truck do it's thing, diesel trucks even with 6 gears do a bit of gear hunting in hills, even my buddy's 800hp/1300tq Cummins 3500 dually. More gears = more hunting under partial loads, factor your lower redline and lower rpm torque band, and now you understand why it's doing that.

Or sell your diesel and really complain about gear hunting in hills.

I actually have the 4.10s with the manual transmission. It's a Rubicon.

I'd still stick to 4th and see how that changes things. I actually got slightly better mpgs with cruise in 4th on the highway between 55-70mph than I do using 5th and downshifting manually as needed for hills, then returning to cruise after shifting, OR staying in 5th on the highway at the same speeds.
- 5th does NOT like being below 2500rpm for acceleration, not with 3.73s anyways.

In all fairness it's impossible to nail what a standard MPG number looks like for Gladiators, especially lacking details, because the variables in tire sizes, gearing, suspension, driving habits, optional equipment ike lights, racks, overland tents etc is infinite. When I got my Overland with street LT tires I was getting 20s. Then I added lights and lost a mile or two. When I switched to 34' AT's the mileage went down to the high teens and when I added the leveling kit it went to mid teens around town and 17-18 highway and 8th gear was just a wish, even on flats. So even with the same car and same driver it was a changing evolutionary game.

In summary, trying to look at just numbers without knowing if they come from a guy driving like grandma on 31" thin LT tires vs some dude running a Sport with a 4" lift and 37" Mts gunning from one light to another is kind'a useless.

When I report my MPGs, I have a 6 speed, 3.73 gears, 255 MTs, and live in rolling hills where the posted speed is no less than 45 but generally 55mph, with stop signs at almost every intersection or a sharp turn dropping speed to below 15mph, just to accelerate back up to 45-55 up a hill.
-Here I see roughly 15-18mpg, and with more consistent highway (still rolling hills, but 55-65mph zones, and rarely slow below 45) I see 17-21mpg (closer to 18-19.5mpg).
-Stock 2021 Willys w/ manual transmission and 49k miles.

 

[Mud Pie]

Not all Jeeps get bad mileage.

I used to do those "trick pics" with my Renegade. I'd brag to my buddy that drives a Taco and send a pic of me getting over 45 mpg. But I used to crop the pic so he couldn't see the full gas tank....

With the 9 speed tranny it had, I did get +/- 35 mpg, though. Hated the vehicle, hated the Tiger Shark engine even more, but it was decent on gas.

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