Declining diesel mileage

[zouch]

hi Norma!

i would bet that you got your best mileage on the first drive because you were driving it more gently as you were still getting used to it. after that, you've been driving it harder as you've become more familiar with it. (these things are admittedly fun to drive hard, but it's going to cost you if you do.)

frankly, your best is worse than what i got when mine was stock, but there are many variables to fuel economy, the biggest one being what you do with your Right Foot.
as somebody else pointed out, fuel consumption increases dramatically with an increase in top speed; think exponentially. (i see better MPG in lower-speed traffic than i do with the cruise on at Calif hwy speeds.)

FWIW, i typically keep the tire pressure in the mid-30s.

enjoy!

Hi. I just love my 2022 Jeep diesel. That being said, my mileage seems to be declining. On the first trip home from the dealership (about 200 miles) I got 26.9 mpg. I had hoped for 30 (haha) but my husband was in disbelief that I got so good. When I got home I lowered the tire pressure from 38 to 34. The next tank I got 25.5 on the highway. Was averaging 22-23 in town. I got about 25 on the highway for the next tank also but the fourth full highway miles was 24ish. This last highway trip I got 22 on the way there and checked it on the way back and got 23.5. The def is in the 60% full range. I have done no modifications. My driving remains the same. I admit though I do like to be one of the fastest on the road. I guess I expected the mileage to get better over time or at least remain close to the same. NOT go down. Anyone else have this happen or can explain why this is happening and if there is anything I can do? I also a couple weeks ago had the fan come on at a weird time and stay on until I pulled over and shut the Jeep off. It did it one more time then hasn't done it since. I'm describing as a fan noise since I assume that is what it is and it is LOUD! I'm a new Jeep owner so I have no experience with them or diesels. My husband tends to think I hear unnecessary noises but I don't. He took my Jeep to work today and thinks it sounds the same. Help!

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[IllinoisChris]

I swear when I see some of these claims of 25-27 mpg my head spins. I haven't seen that. Im just at 5200 miles and the average mpg for those miles is right at 21. Im in Illinois, right in the heart of flatlands lol.

 

[Deleted member 59498]

I swear when I see some of these claims of 25-25 mpg my head spins. I haven't seen that. Im just at 5200 miles and the average mpg for those miles is right at 21. Im in Illinois, right in the heart of flatlands lol.

Yeah I am in the 21ish zone myself, I generally run about 70mph maybe 67 if I think the radar is out on the highway.

 

[grimmjeeper]

I swear when I see some of these claims of 25-27 mpg my head spins. I haven't seen that. Im just at 5200 miles and the average mpg for those miles is right at 21. Im in Illinois, right in the heart of flatlands lol.

A lot of it is how you drive.

In town I usually get low 20s. On the freeway which can get up to 80+ out west, I don't get a lot better. But on the back roads where I'm cruising long distances at around 60-65 I've seen 30.

 

[Gorilla57]

A lot of it is how you drive.

In town I usually get low 20s. On the freeway which can get up to 80+ out west, I don't get a lot better. But on the back roads where I'm cruising long distances at around 60-65 I've seen 30.

That’s what I get in my 1500 with the diesel. Love this motor and the MPG. I get 12mpg towing the buggy on the trailer at 70mph.

 

[Antonio]

I swear when I see some of these claims of 25-27 mpg my head spins. I haven't seen that. Im just at 5200 miles and the average mpg for those miles is right at 21. Im in Illinois, right in the heart of flatlands lol.

Honestly 27 can be done I’ve even seen the dash mpg reach 30 a few times, but it’s not fun driving I average 23 DD or so

 

[Feb14bgirl]

Yeah I am in the 21ish zone myself, I generally run about 70mph maybe 67 if I think the radar is out on the highway.

Well, this makes me not feel like the Lone Ranger. I did manage to get 24.5 in city only driving this past tank. I never go by what the screen says because it said I got 25.9 that tank. Anyway, I leave for Missouri Thursday and will have several highway tanks to check. I bumped up my tire pressure to 37 like when I drove the Jeep home. Fingers crossed I am able to get what I did on the way home from the dealer.

 

[Ratbert]

I swear when I see some of these claims of 25-27 mpg my head spins. I haven't seen that. Im just at 5200 miles and the average mpg for those miles is right at 21. Im in Illinois, right in the heart of flatlands lol.

Mine was giving me 26 / 25 on a trip to / from Ouray CO this summer. That's before I added the massive roof rack, but it included 37s, 4.63 gears, 2.5" lift, aluminum skids, heavy AF sliders, Warn winch, SOT open as much as possible, etc.

The big thing that guzzles fuel is speed. A huge chunk of that trip avoided interstates, so most of it was under 60mph.

Overall (with the massive roof rack) I'm averaging about 20 MPG, but that's including lots of rock crawling where mileage seems to drop off dramatically.

 

[IllinoisChris]

Mine was giving me 26 / 25 on a trip to / from Ouray CO this summer. That's before I added the massive roof rack, but it included 37s, 4.63 gears, 2.5" lift, aluminum skids, heavy AF sliders, Warn winch, SOT open as much as possible, etc.

The big thing that guzzles fuel is speed. A huge chunk of that trip avoided interstates, so most of it was under 60mph.

Overall (with the massive roof rack) I'm averaging about 20 MPG, but that's including lots of rock crawling where mileage seems to drop off dramatically.

Which is even more amazing. I drive it like it’s a Jeep. No heavy acceleration, almost never over 70, pretty much all flat trips so far. All stock JLU Rubicon. I’m not complaining, just always surprises me to hear some of you with such high averages. I did get around 26-27 on the trip home from Pennsylvania when purchased new. Haven’t seen anything close since.

 

[Ratbert]

Which is even more amazing. I drive it like it’s a Jeep. No heavy acceleration, almost never over 70, pretty much all flat trips so far. All stock JLU Rubicon. I’m not complaining, just always surprises me to hear some of you with such high averages. I did get around 26-27 on the trip home from Pennsylvania when purchased new. Haven’t seen anything close since.

Elevation, humidity, and temperature all impact it as well.

 

[ALeeL]

You can loose up to 20-25% fuel mileage in colder weather due to the increase in air density of colder temperatures. It is worse for less aerodynamic vehicles with a higher drag coefficient. I see it every year in my fuel records between my Ram 2500 diesel and BMW diesel. Both of them loose some mileage as the temps get colder, however, the truck looses a greater percentage since it has the drag coefficient of .40cD and the car is around .27cD which is on the low end for a production vehicle. The Jeep JL is .45cD so it should take a slightly bigger hit percentage wise than my truck.

 

[Elf]

All of you are doing much better than me. My '21 JLU from AEV is averaging 18 mpg. Has only 6250 miles so far, I do drive almost daily. I don't care though, love this Jeep.

 

[BDinTX]

All of you are doing much better than me. My '21 JLU from AEV is averaging 18 mpg. Has only 6250 miles so far, I do drive almost daily. I don't care though, love this Jeep.

What diff gears does that come with? The gas ones had 4.56 like the XRs if I'm not mistaken.

 

[Ratbert]

What diff gears does that come with? The gas ones had 4.56 like the XRs if I'm not mistaken.

I'm thinking they all come with 4.56s. Mine (diesel) was an anomaly and came with 4.63s due to supply constraints.

 

[nsfw_andy]

I have a 2022 with 12k miles currently. My mpg did increase slightly by 2-3mpg over time, im guessing there is a break in period.

The first 8k miles was on stock tires and lift, I averaged about 24-25mpg day-to-day going to work and back, mostly freeway driving at around 65-70.
On long highway road trips I can pump those numbers up to about 29-31mpg if I keep it around 70mph.

I have since installed heavy 37s w/ beadlocks and 3" lift and have been driving it for 4k miles already.
Average day-to-day mpg went down to about 20-21 mpg now, and about 24-25 on long highway road trips.

I also try my best to remember to use fuel treatment (Hotshots EDT) on every fill up.

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