Hi All, Newbie here...
Just got my wife's stock 2000 4.0 WJ passed to me with 201K miles. Currently rebuilding the i6 engine. I am planning a 4" lift and want to put larger wheels/tires on it.
Not sure how wild to go yet as I want to consider what the MPG may be with
31", 32", 33" tires. It will be my daily driver.

Any MPG experiences with a 4.0 WJ with larger tires?

Thanks,
Buggutz

 

it makes a big difference what gears you have. i am gonna say with 33's and 4:10 gears you are looking at 13-15 street, and 15-17 highway

 

I've got 33X10.5s with 4.10 (manual trans) and average 18+ mixed driving. Gearing helps a lot, before the change it was 15 of course with the near stock tires that came with it I averaged 20.

 

the Grand Cherokee WJ's weigh about 600lb's more then an XJ, and they have that all time 4x4 crap

 

I just put 30" tires on with a 2.5" lift, with no change to gearing and I have consistently been getting 1-2 mpg less than I was getting all stock.

 

not all wjs have fulltime 4x4, most actually dont. he is right though, wjs will be a different outcome in mpg. my sisters wj went from 18 mpg stock to 12 with 4 inch lift and 33s. She has the v8 though.

 

yes but they have the aerodynamic co efficiency of a rounded brick versus the square brick. But in all seriousness just comparing before/after tires and gearing to show how gears help.

 

I'm running a 3.5" lift with 31's and noticed a significant drop from 240 - 260 miles a fill up, to 200 - 215 miles a fill up .... but I found it's all on how late I am for work. If I'm runnig early I can go 60mph and get up to 230mph a tank .... mostly freeway miles too. The skinny peddle has a big effect no matter what set up you have.

 

hey could you tell me how to set up my XJ to do 230mph? Any death wobble above 150? haha just messin with ya..

 

4.56 n 33's bout 5.5 of lift and down to 10 mpg if im lucky, on a good day down hill! burnd thru 20 gallons almost on my trip to walker n back. best milage i ever got is parked in the yard. need a tow rig n trailer!

 

Something's wrong then, I get 16mpg on 33s 4.5 lift and 3.55

 

Buggutz,

Here is the straight skoop. With a Jeep vehicle running the 4.0 I-6 engine and an AW4 automatic transmission the following is what you will need to get optimum mileage and to keep your engine in it's happy power making RPM range. BTW, partime or fulltime doesnt matter in a XJ , ZJ. they donnot have lock out hubs and the front running gear all spins all the time whether in 2WD or 4WD.

stock - 30" = stock 3.55 axle gears will be fine.
31 - 32" = 4.10 gears
33 - 34" = 4.56 gears
35 - 36" = 4.88 gears

At this point you have to do some serious thinking. You can't get gears lower than 4.88 for the Jeep D30 or the ChyCo 8.25. Also for tires bigger than 35s you really should start looking into bigger stronger axles or at least putting up the cash for Chromo shafts and other serious upgrades so the axles will live with the bigger rubber.

I have run the following combination on my 91 XJ for about 4 years now....4.0 HO motor, AW4 auto tranny, D30 front and D44 rear with 4.56 gears, lockers front and rear and 33" tires. My Jeep gets a solid 18mpg on the highway.

 

Along with that quality of fuel, tire width and air pressure also make a big difference. I get a 2-3 mpg difference running 10.5" tire vs the 12.5" on 33s with 3.55 gears. I get 10-12 city, 18 hwy, and 10-12 wheeling, no matter how I drive Ive been debating getting 4:10s or 4:56s but now I wonder if it will improve mileage...

 

She just hovers after 190
mph ... mpg I gues there is a big difference!!

 

ive gone thru everything no leaks new injectors filter most of the sensors got a cold air damn t body spacer banks t tube header???????? ive always thought theres somethin wrong but i cant find it?????