MPG compartively?

Hi guys! Some questions I have for those who payed attention to their MPGs. I realize if your gunna own a lifted xj you need to understand MPGs are gunna be bad. But I am in need of some "reference" regarding my situation.

I had a 97 XJ 4.0 AX15 manual with 35" tires on 3.07 gears. I have no idea what my MPG was but I would love to know what that MPG most likely was. I know it wasn't the right gear and trying to climb slowly required fancy foot work but for mudding it wasn't too bad (higher RPMs). On the road it wasn't bad at all, I still used 5th despite others warning me it was useless. Granted I only used 5th on flat highways lol. So stupid me sold my XJ only to miss it like a crack addict misses his fix on day 3 of rehab lol. So now I'm on the market for another one!
I found a 99 4.0 XJ with AW4 trans and 35" tires with 3.55 gears. He tells me only gets about 11mpg with it. Either way I'll most likely wind up buying it and regearing it in the distant future, but I'm curious as to how his mpg would compare to the mpg of my old xj. One more factor to throw in is that I'm moving to Florida (where this XJ I'm looking at is) where the roads are flat and open with stop and go here and there as opposed to where I drove my old XJ (Massachusetts) everything was hilly windy 40mph max stop and go city driving. Partly why I'm excited to be living in Florida soon lol.

35" tires 3.07 gears manual:
City mpg: ???
Highway mpg: ???

35" tires 3.55 gears auto:
City mpg: 11
Highway mpg: ???

Thanks so much!!! It's greatly appreciated!

I have 31 with 3.07 and AX15. Is not what you're asking for but maybe it helps.

In city (lots of stop and go): 11MPG
In highway: 18.8MPG (at 65MPH).

I have a 5.5 lift.

Wow that low on 31s???? When u say city do u mean like downtown Brooklyn traffic or like Florida city traffic (a red light every half mile)

i have a 7" lift, 37's, 5.13 gears, and get about 17 on the highway.

A lot of people never see better than 12 no matter what.

the 4.0 doent like to work real hard, so deeper gears will get better mileage (some tards argue this).

What really matters is having things properly tuned up, sensors in good shape, etc etc.

I'm a mechanic and so was the owner of the new jeep. I plan in sea foaming it, running a hi-flow exhaust, fan fed cold air intake, new plugs etc...


Would different injectors yield better mpg? A bored throttle body will give better acceleration do theoretically that shouldn't effect mpg if you drive it like an old lady?

a bored throttle body will give more top end if you have an engine built to take it. some guys claim crisper throttle on a stock motor with it, but that has not been my experience.

don't forget o2 sensor, coolant temp sensor, MAF sensor, IAT..

On 33"'s with 4 1/2" lift, 3.55 gear, AW4 loaded 10-11mpg re-geared to 4.56's now 15-16mpg gained an easy 5mpg. I have a lot of drag on mine roof rack, big bumpers, winch, loaded with recovery gear.

Obviously motor condition varies but it almost seems like some motors are more green than others lol. My friend had 32s with 3.07s stock and got 10 everywhere...

Back to the original question, what's a good guess on mpgs for 35s with 3.07 manual city and highway?

Also, is there any alternative to regearing the axle? Like some sort of yoke end portal or something in the drivetrain from the driveshafts up? Just wondering

4.0, aw4, 4.5 inches of lift, 35s, 4.88 gears, corrected speedo.

I track my fuel mileage every fill up and get an average of 16.7 mpg. I'd say about 80 percent city driving.

I<3Mud said:

Also, is there any alternative to regearing the axle? Like some sort of yoke end portal or something in the drivetrain from the driveshafts up? Just wondering

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there isn't. i can think of a dozen technical reasons why that wouldn't be feasable anyways.

regearing is fairly simple and relatively not all that expensive, although the most expensive thing people with smaller jeeps do to them - not by a long shot the most expensive thing people with well built jeeps have to accomplish.

if you're worried about trying to avoid regearing your axles, building a jeep for 35's is certainly not for you.

cal said:

there isn't. i can think of a dozen technical reasons why that wouldn't be feasable anyways.

regearing is fairly simple and relatively not all that expensive, although the most expensive thing people with smaller jeeps do to them - not by a long shot the most expensive thing people with well built jeeps have to accomplish.

if you're worried about trying to avoid regearing your axles, building a jeep for 35's is certainly not for you.

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I have no problem regearing. As stated previously i intend on doing it anyways in the future, i was just curious if there was any newer technologies out there.

it wouldnt really be newer so much as different, but the problem you would have then is *extreme* load on your driveshafts. You'd be putting 50%+ more torque them, adn they woudln't hold up.

Samurai guys have that problem, they do transfercases with like 8:1 low range and 20% reduction high range.. but then they gear up driveshafts and mounts.

Also, our driveshafts are too short for tall lifts as it is, so adding anything else inline would drastically hinder lifting your jeep to fit any tire warranting a regear.

Also, it would just be stupid.

dwreck30 said:

4.0, aw4, 4.5 inches of lift, 35s, 4.88 gears, corrected speedo.

I track my fuel mileage every fill up and get an average of 16.7 mpg. I'd say about 80 percent city driving.

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Does it scream on the highway? what RPM?

Thanks!

13.5-14MPG MPG loaded to and from the mountains loaded and pushing it hard. Sometimes unloaded going to and from the Bay Area I will get 16-17MPG on flattish freeway with no real load. I tune it (plugs, plug wires, cap, rotor, acetone, flush oil and cooling system and all other fluids, clean TB, air filter, fuel filter, sea foam intake, check all vacuum lines, clean all grounds, and replace o2 sensor every year ) and test/replace/check all sensors twice a year as needed. I currently have a bad exhaust leak and I Know that is doing something bad of the MPG since before it I was getting closer to 15-17MPG . And a bored out throttle body and high flow exhaust and long tube header(i hate pacesetter though but whatever at this point) . I usually somehow kill like 2 -3 TPS a year (hoodvents+ water+napa echlin TPS = kill TPS)

37 MTRs(old style) black steelies no bead locks
5.13s
25 PSI on the street max (often times 20 PSI or less )
rig probably weighs 5000 + pounds with all the tools and a few people in there that much more. Tons of extra steel. Tons of tools and spares. Big Beer cooler.


I had a buddy with 31s and 3.07s and consistently got 21MPG everywhere he went (went to 4.10s and stayed close to the same)

I<3Mud said:

Does it scream on the highway? what RPM?

Thanks!

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what do you consider screaming on the highway?

a stock 4.0 is supposedly happiest around 2700 rpm's. I run mine around 3,000 on the freeway and it loves it.

cal said:

it wouldnt really be newer so much as different, but the problem you would have then is *extreme* load on your driveshafts. You'd be putting 50%+ more torque them, adn they woudln't hold up.

Samurai guys have that problem, they do transfercases with like 8:1 low range and 20% reduction high range.. but then they gear up driveshafts and mounts.

Also, our driveshafts are too short for tall lifts as it is, so adding anything else inline would drastically hinder lifting your jeep to fit any tire warranting a regear.

Also, it would just be stupid.

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Lol. Well i do appreciate the explanation... doing some research i found the "Black Box" which goes on the trans and transfer case as a planetary ad on, but price wise your better off doing a full rehear anyways...

Like i said i was just curious

Doesn't scream at all. I want to say I'm at around 2300-2400rpm at 65mph. Haven't really paid attention in a while. I've had VWs that cruised at over 3000rpm on the highway bone stock.

I<3Mud said:

Lol. Well i do appreciate the explanation... doing some research i found the "Black Box" which goes on the trans and transfer case as a planetary ad on, but price wise your better off doing a full rehear anyways...

Like i said i was just curious

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well, and that only works in low range - it doesnt help you on the highway, or in high range - which is where regearing makes the biggest difference.

I<3Mud said:

Wow that low on 31s???? When u say city do u mean like downtown Brooklyn traffic or like Florida city traffic (a red light every half mile)

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Where I live some streets have lights at every corner and is hard to find 3 synchronyzed in a row. The blocks are about 100 yards, so in a mile you can go and stop 7 o 8 times. Add narrow streets and third world traffic. I guess you get the picture ;-)