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What MPG are you getting?

Ticks

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Just figured out yesterday I’m at about 13mpg.
4.0L, NV3550, 4”SL w/ 33x10.5s, …3.07 gears…
I’m learning fast I need to regear…

33"s and stock gearing will kill mpg. I know from experience of doing this with a XJ 3:73 and a MJ 3:55 both went down drastically, both were 4.0L 5 speeds.
That is why I left the TJ alone for now since thatis my DD.
 

Pantera99

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Sep 2, 2022
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Gilbert, AZ
So experimenting with running the rpms up this morning. Gotta say wow, guess thats where all the power is. Coming up around 3000 rpm she is definitely alot more fun. I just assumed it'd be sucking gas like mad. Stayed in 4th up till 60 mph but then at 60 in 5th she's barely at 2k rpm. I imagine 4.11 or 4.56 gears would help alot.
 
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HandOverFist

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Seems to be a lot of variables here. My buddy has a Rubicon with 4.10's, 35" tires, auto and heavily loaded with accessories...claims he can squeak out 20mpg if he stays below 60mph and 17mpg is the normal. His is a 2012 though so can't directly compare to our inline engines. Also has a 5 speed auto in it.
 
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James9100

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May 3, 2021
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Saskatchewan, Canada
33"s and stock gearing will kill mpg. I know from experience of doing this with a XJ 3:73 and a MJ 3:55 both went down drastically, both were 4.0L 5 speeds.
That is why I left the TJ alone for now since thatis my DD.

It actually makes that much of a difference? Some guys seem to say it makes a minimal difference, some say it’s a big difference.
Going from 3.07 to my planned 4.10 is a pretty big jump so I’m hoping it’ll make a noticeable increase in mpg.
 
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HandOverFist

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How many miles would it take to recoup the average cost of re-gearing assuming there is an increase in mpg? Just doing the math in my head it would seem to be at least 75K miles...something to consider.
 
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Ticks

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Ct
It actually makes that much of a difference? Some guys seem to say it makes a minimal difference, some say it’s a big difference.
Going from 3.07 to my planned 4.10 is a pretty big jump so I’m hoping it’ll make a noticeable increase in mpg.

Oh yea, you'll see on them long grades on freeways and such. 5th gear is pretty useless even on flat.
 
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NashvilleTJ

I miss the snow...
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How many miles would it take to recoup the average cost of re-gearing assuming there is an increase in mpg? Just doing the math in my head it would seem to be at least 75K miles...something to consider.

Mileage is absolutely not the reason for a regear - it’s just a very minor side benefit.
 
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XCRN

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Jun 1, 2020
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Springfield OH
Currently on 32s with 3.07 and a cammed 5.3. Best I ever got was 16.5 (which is used by multiplying my odo miles by a GPS confirmed odo factor) shortly after increasing my exhaust from 2.25 dual to 2.5in single to 2.5in dual to 3in single and using 1-5/8 header primaries. I dropped to 15ish after swapping headers to 1-7/8 primaries. I have the instant readout of fuel flow and noticed an increase of about 3lb/hr at 55 after swapping headers, so I am thinking of getting a more restrictive muffler to mimick the smaller headers. My next project is swapping in a Dana 44 with 3.73 and going away from the Holley Terminator X to a stock PCM which I think might get me closer to the 20s. I am down sizing my tires to 31s with lighter wheels since its a daily driver.
 

MikekiM

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If you’re drivings manual, watch your shift points and coast in neutral a lot. You can't get inflated, though unsubstantiated numbers using smoke and mirrors. Kind of like the politicians do. :p

How many miles would it take to recoup the average cost of re-gearing assuming there is an increase in mpg? Just doing the math in my head it would seem to be at least 75K miles...something to consider.

Can't see your profile info so not sure if you're an auto or manual...
If you see any mpg improvement after a re-gear, it's a bonus and shouldn't be the reason for re-gearing. Spend your money elsewhere if improving mpg is your goal.
 

Jerry Bransford

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All flatland round here which is why I’m planning 4.10 rather than the recommended 4.56.
But ya even so 5th drops the RPM’s waaay too much.
The recommended 4.56 for 33's and 5-speed is made for a reason, you'd be slightly undergeared with 4.10 enough that you'd hate your 4.10 decision. Even on flat terrain. I know because I did that stupid effing mistake 20 years ago when I didn't listen to all the recommendations for 4.56 for my then-new 33" tires and instead only regeared to 4.10. I was kicking myself every day afterwards for the several years until I got to 35's and happily regeared to 4.88.
 

Athena

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Feb 8, 2022
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Chesapeake, VA
My '01Sport is more or less stock, 5 speed manual too. Not sure about my city miles, likely 15 mpg or so, highway at 55-60 I had been consistently getting 20.3 mpg actually. I use the website fuelly.com to help me track my mpg.

1664372852871.png

I edited this post to add a fairly recent and decent res image of my Jeep as I have it setup. I did remove the rear seat and some other stuff. I have really crappy looking OEM 15 rims but my tires are fairly sturdy and AFAIK, definitely not the OEM size tire. I always try to coast to red lights when I can and not to accelerate too heavy. For me, my goal when driving is to try to get my car into 5th gear as soon as I'm able to, which I find approx 45 MPH I can shift up to 5th but if I slow down for any reason, I'll have to downshift since my revs are fairly low 5th gear at 45.

DSC01493.JPG


IMG_20220209_154116.jpg
 
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HandOverFist

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If you’re drivings manual, watch your shift points and coast in neutral a lot. You can't get inflated, though unsubstantiated numbers using smoke and mirrors. Kind of like the politicians do. :p



Can't see your profile info so not sure if you're an auto or manual...
If you see any mpg improvement after a re-gear, it's a bonus and shouldn't be the reason for re-gearing. Spend your money elsewhere if improving mpg is your goal.

I threw that question out for the masses, not myself. Mine is an automatic with 33" tires and is just the way I purchased the vehicle. I suspect there are many like myself that only use their Jeeps for simple transportation and rarely offroad. Bet there are tons that were purchased with larger tires already installed like myself. No doubt lower gears would make it more responsive and "might" improve mpg, but the cost really can't be justified simply for mpg's sake alone...this was the sole point of my post. The break-even time frame is very long for mpg gains.

Yes, you could remove the previous owner installed lift kit and larger wheel/tire combination, but that puts you right back in the same spot as above. One would likely spend just as much money as a re-gear assuming you don't have the stock components to go back with. There simply isn't anything else you can throw money at on these vehicles that will increase mpg in any significant way.
 
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JustDandee

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Sep 26, 2022
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Nampa, Idahoooo
A couple of observations: Aerodynamics come into play over 55 MPH- With any of my trucks the MPG penalty starts to show at 65MPH more. The jeep I recon it starts close to that 55 mph mark with that box shape. Looks like the OP has mud terrains/steel rims? That could be a heavy combination so rotational weight is factor and rolling resistance. If MPG was a goal, moving to an A/T tire and lighter rim would help. Keep expectation's reasonable 1-2 MPG at best.

I am three tanks into my owner ship @ 16.43 average on 30" tire. I bought the manual just for this reason, I think a little higher MPG is achievable over a automatic. One benefit I try to keep in mind when I build up - higher MPG means having a longer range on the factory tank when tooling around the back country.
 
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Pantera99

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Sep 2, 2022
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Gilbert, AZ
Wow ok I totally get the whole 5th gear is useless now. Drove this morning as if I didn't have a 5th gear & it was great! Less shifting, more responsive, 58 mph was turning 2500 rpm in 4th. Hard to get much faster than that in congested Phoenix rush hour. We'll see how this tank goes. Grabbed Sams Club gas last night as prices are spiking again, Sams was $4.19, everything else is $4.39-4.59!?!! Thought oil was crashing down?!!