Diesel mpg's back after 35's??

[jimhaleii]

2021 jl unlimited sahara altitude diesel, 3.73 gear, oem dana 44's and heavy duty 8sp auto.

Was getting 32 mpg on hwy and averaging 28 mpg all around when stock.

Just picked it up after doing mopar diesel specific lift with bilstein reservoir shocks, yeti front and rear adjustable trackbars, yeti tierod assembly, yeti draglink, yeti sector shaft brace, and relocation bracket, upgraded fox steering damper and brackets, quadratec hd ball joints, 22x10 thret offroad monarch wheels wrapped in 325/50r22 Nitto Recon Grapplers.
TAZER programmer and jeep has had new tire diameter set.

Drives great, tracks straight and true, no wobble or wandering at all... no noticeable loss of power. LOVE IT.

But it does seem more sensitive to inclines and the mpg is suffering more than I wouldve thought from the diesel. I am now getting 28 ish on hwy and averaging 23 - 24. If I geared at 4.10 could that help mpg? Ps. Some before and afters:

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[Ratbert]

That's still pretty damn good mileage.

Is your build intended for rock crawling or just for looks? Your equipment list implies rock crawling, but your sidewalls look awfully short for that.

 

[driventoadventure]

Your tires are about 50% wider than your previous tires, which could potentially double rolling friction. Your tires are also going to be equally as much heavier. The higher ride height will add substantial drag. You're getting about what Rubicon trims get because you're running nearly Rubicon weights and ratios. Higher gearing might get you 5% more, but really you're right on target with expectation... Getting a GDE tube might get you 15% based on what others have started, but you're never going to get close to your previous economy because there is very considerably much more systemic resistance.

 

[Terpsmandan]

That and the tires being uncovered are are going to add some drag as well. I am getting 22-25 on my JLURD on 37" KO2's. Mopar lift and GDE tune. No regear.

 

[Wrangler man]

That's still pretty damn good mileage.

Is your build intended for rock crawling or just for looks? Your equipment list implies rock crawling, but your sidewalls look awfully short for that.

Fully agree with Ratbert
If you still can you should strongly consider dropping those wheels and tires for something that compliments and is intended for that suspension that you had installed. Even if you don't ever rock crawl your trail ride, dirt road experience with that wheel-tire combo and Bilstein shocks won't be the most pleasant one. Those are not your typical 35s. A set of 37s on a 17-in wheel would most likely render you similar MPG. Aired down to 12 PSI off-road would give you far superior performance and smoothness of where you sit now. Not sure you would be far off from being the same weight in a 17 x 12.5 x 37. It's not the same car show effects as what you have now but it will definitely give you great off-road abilities and compliment that suspension system very well. Bilstein makes quality shocks but they're lower end monotube shocks give a uncomfortable ride. Absolutely love your Jeep color choice. The orange looks super cool. Ohlins has come out with new JL bolt on by pass shocks that I intend I'm putting on my rig this November that would actually color match your rig and give you a Superior ride. They are adjustable for rebound and compression and won't break break the bank, sitting at a very comparable performance level that you already have with the Yeti setup. Giving great performance and ride. Good luck.

 

[Hard Rock Jeep]

Hello from Nashville. If you regear to 4.10, you will be turning more RPM all the time. This is the point of regearing, to get you into higher RPM's with your larger tires. (Larger tires take less RPM to get you the same distance.) We regear lower torque engines because we need to get the RPM's up to get to the greater torque band. But you have a diesel. You get 442 #/ft of torque from the time the wheels start turning (about 1400 RPM considering the torque converter action). With your 34.8" tires at 70mph the drivetrain math says you will be turning 1691 RPM with your 3.73 gears. At 4.10 you will be turning 1858. There are a lot of factors in why we get the mileage we get, but all things considered, you will get lower mileage with the 4.10.

I have a diesel JL with 37's and have no intention of regearing. We have massive torque and do not need to regear.

 

[AC77]

2021 jl unlimited sahara altitude diesel, 3.73 gear, oem dana 44's and heavy duty 8sp auto.

Was getting 32 mpg on hwy and averaging 28 mpg all around when stock.

Just picked it up after doing mopar diesel specific lift with bilstein reservoir shocks, yeti front and rear adjustable trackbars, yeti tierod assembly, yeti draglink, yeti sector shaft brace, and relocation bracket, upgraded fox steering damper and brackets, quadratec hd ball joints, 22x10 thret offroad monarch wheels wrapped in 325/50r22 Nitto Recon Grapplers.
TAZER programmer and jeep has had new tire diameter set.

Drives great, tracks straight and true, no wobble or wandering at all... no noticeable loss of power. LOVE IT.

But it does seem more sensitive to inclines and the mpg is suffering more than I wouldve thought from the diesel. I am now getting 28 ish on hwy and averaging 23 - 24. If I geared at 4.10 could that help mpg? Ps. Some before and afters:

very nice color and setup, i get about 24-28 after my setup of wheel n tires, 33's on 20s

Afe air intake and Afeblade runner piping with Derringer tuner, its awesome

 

[BuffaloBill]

I regeared from 3.73 to 4.10 after changing wheels/tires to 35s. If my mpg changed with the regear, it was slight. With the 4.10s it generally averaged 26mpg when my trip lenghts were 1/2hr. Since retiring I seem to have more frequent shorter trips and the average has dropped to 24-25. On a longer road trip traveling 60mph, during warm weather, it will do 27-28mpg. I don’t have a suspension lift.

I like the 4.10/35” combo as it will hold 8th gear @ 60mph over modest hills or headwind, shifting less frequently than with the stock 3.73.

 

[Deleted User 38384]

2021 jl unlimited sahara altitude diesel, 3.73 gear, oem dana 44's and heavy duty 8sp auto.

Was getting 32 mpg on hwy and averaging 28 mpg all around when stock.

Just picked it up after doing mopar diesel specific lift with bilstein reservoir shocks, yeti front and rear adjustable trackbars, yeti tierod assembly, yeti draglink, yeti sector shaft brace, and relocation bracket, upgraded fox steering damper and brackets, quadratec hd ball joints, 22x10 thret offroad monarch wheels wrapped in 325/50r22 Nitto Recon Grapplers.
TAZER programmer and jeep has had new tire diameter set.

Drives great, tracks straight and true, no wobble or wandering at all... no noticeable loss of power. LOVE IT.

But it does seem more sensitive to inclines and the mpg is suffering more than I wouldve thought from the diesel. I am now getting 28 ish on hwy and averaging 23 - 24. If I geared at 4.10 could that help mpg? Ps. Some before and afters:

I've been averaging 23 MPG on average on my mostly stock build, and just got a PCM tune and am driving even more recklessly and somehow I'm still getting 27 MPG average.

?

Maybe it's just me, but I feel like them 22-in rims are weighing you down. Probably should get rid of them and get some 17-in beadlocks. You're going to want more sidewall for off-roading anyways.

 

[jimhaleii]

That's still pretty damn good mileage.

Is your build intended for rock crawling or just for looks? Your equipment list implies rock crawling, but your sidewalls look awfully short for that.

Mostly looks, But it gets taken off road on job sites and mild trails.
I put all of the beefier stuff under it because right after i bought it, it had a couple of incidences of death wobble over bumps at hwy speeds... and it was bone stock, so i replaced all of the cheap hollow parts with what i felt was the best available. And now, i have a good foundation to build from, if i want to beat on it 1 day, its ready!

 

[jimhaleii]

very nice color and setup, i get about 24-28 after my setup of wheel n tires, 33's on 20s

Afe air intake and Afeblade runner piping with Derringer tuner, its awesome

Thanks! I love this thing and the color...Yeah im ordering the derringer too! Think imma need 4.10's too ? ? ?

 

[speedymart]

I'm gonna be real, putting 22's on your jeep is just something else. You just massively increased the driveline weight for almost zero performance benefit. Your MPG is going to suffer for it, not much you can do. I'd imagine it's lighter with less sidewall though

 

[jimhaleii]

Your tires are about 50% wider than your previous tires, which could potentially double rolling friction. Your tires are also going to be equally as much heavier. The higher ride height will add substantial drag. You're getting about what Rubicon trims get because you're running nearly Rubicon weights and ratios. Higher gearing might get you 5% more, but really you're right on target with expectation... Getting a GDE tube might get you 15% based on what others have started, but you're never going to get close to your previous economy because there is very considerably much more systemic resistance.

Yeah, thats what i figured...ill hit it with gears and a tune or derringer setup and rock it!
Next tires im gonna go with 35x12.5's, 1" less width and therefore less contact friction...just thought these 325/50's were SICK looking!
Thanks for the great info!

 

[AC77]

Thanks! I love this thing and the color...Yeah im ordering the derringer too! Think imma need 4.10's too ? ? ?

have a brand new one for sale ....

 

[jimhaleii]

Fully agree with Ratbert
If you still can you should strongly consider dropping those wheels and tires for something that compliments and is intended for that suspension that you had installed. Even if you don't ever rock crawl your trail ride, dirt road experience with that wheel-tire combo and Bilstein shocks won't be the most pleasant one. Those are not your typical 35s. A set of 37s on a 17-in wheel would most likely render you similar MPG. Aired down to 12 PSI off-road would give you far superior performance and smoothness of where you sit now. Not sure you would be far off from being the same weight in a 17 x 12.5 x 37. It's not the same car show effects as what you have now but it will definitely give you great off-road abilities and compliment that suspension system very well. Bilstein makes quality shocks but they're lower end monotube shocks give a uncomfortable ride. Absolutely love your Jeep color choice. The orange looks super cool. Ohlins has come out with new JL bolt on by pass shocks that I intend I'm putting on my rig this November that would actually color match your rig and give you a Superior ride. They are adjustable for rebound and compression and won't break break the bank, sitting at a very comparable performance level that you already have with the Yeti setup. Giving great performance and ride. Good luck.

Wheels and tires gotta stay, love the looks plus they set me back about 5k, lol, its more for show with only mild trails for now. The bilsteins are great on road and they are reservoir style so lotta travel if i need it. Ill check out those orange shocks youre doing and maybe try them out later, thanks brother!

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