$hity ga$ milage

[Fred85]

o2 sensors
injectors
tps
cps
fuel pump
get a compression test

i'd check these first, if you have the ability to.......fix the exhaust manifold first, like said above

 

[MudDawg]

Either gear it or get rid of the 35s...dont waste your time or money on 4.10 or 4.56 unless of course you have a 8.25 chrysler rear...go straight for the 4.88 gears..minimum...or pull off the 35s and put on some 29s. You cant imagine how much difference there is both in fuel economy and performance.

Listen to the old Dawg.

 

[Kittrell]

Either gear it or get rid of the 35s...dont waste your time or money on 4.10 or 4.56 unless of course you have a 8.25 chrysler rear...go straight for the 4.88 gears..minimum...or pull off the 35s and put on some 29s. You cant imagine how much difference there is both in fuel economy and performance.

Listen to the old Dawg.

The old Dawg is slippin', he has 31s...................:twak:

 

[Starboard M]

Whay do I see all thes guys running 35's and getting 13-15 mpg on stock gears while im running 31 and getting 10 I reacently did major tune up any suggestions why I have stock gears 3.54,d44 rear,d35 front.Ran seafoam changed oil,what else am I missing???

I just want to see your D35 front:wierd:

 

[MudDawg]

"The old Dawg is slippin".....right you are...for the record, my mind is like a steel trap.....rusty and illegal in 27 states...:laugh:

 

[sidriptide]

aside from a mechanical deficiency, your own driving style has a huge effect on the fuel economy you get out of your 4.0L.

my 250,000 mile 90, 4.0,AX-15, 4.56s, 33s gets a solid 14-15 mpg with around-town daily use.. i have a heavy foot. if i get on the highway i get about 17-18.. one thing i want to point out is that if you are running stock gears and larger tires your speedo/odometer is incorrect and you need to figure the error into your math. dont remember what trany you have but an auto in a combination like that will lug more, requiring you to use more throttle. higher RPM has pretty much no real effect on fuel economy. acceleration/low manifold vacuum will use alot more fuel than a faster revving engine with a better tire/gear combination.
i hear sometimes of guys getting 20+ MPG from their XJs. but i think that has alot more to do with driving style and a properly set up vehicle. a few other factors that come into play are fuel quality and even the altitude you live at.
i drove from new england to Utah last may and i watched my mileage the entire way. here are a few of the totals i got at diferent legs of the 5000 mile run which was done at about 70 mph the entire way. these are based on where i bought the fuel.
pennsylvania.. 18 mpg
ohio.... 19 mpg
indiana... 14 mpg!!!! (this big difference was backed up by the two other rigs i was traveling with)
kansas.... 18 mpg
colorado .. 21 mpg!!! (this was westbound beyond denver thru the high passes where the engine literally fell on its face)
colorado... 23 mpg!!!! (this was eastbound toward denver thru the same section)

these mpg numbers are corrected to actual distance travelled, my speedo/odo is off by 22%..

and sometimes the explanation is just "XJs are all different sometimes"

 

[53guy]

I don't know, but I run 35's and 4.56's and get 14mpg with no exhaust leaks and a great running motor and the correct speedo. I drive with a heavy foot around town and do 75 on the highway.......that's why i get crappy mileage, its not the jeep.

 

[SLAYER]

91 PROJECT.
3.55 with 33 1-11 miles in town and 14 highway? That is poop.
SLAYER
4.56 12-15 in town and 18-20 on the highway.
GET SOME GEARS!! heheheheheheheheehehheeheh
btw u prob have em on another one of yer rigs.

 

[Menzenski]

i hear sometimes of guys getting 20+ MPG from their XJs.

I do. Wierd as it may seem, the best mileage I've gotten so far in my XJ has been with 31s and stock 3.07s. I averaged almost 22 miles per gallon on my way out to Massachusetts back in July. I think in general the stock gears are way too tall, even with 225/75R15 tires. If you stop using 5th gear (or stop using overdrive 4th if you have an AW4), I expect your mileage will go up. Now I have 31s and 3.55s, and I don't use fifth. At 65 miles per hour, I'm right at 2500 RPM, which is just about perfect. I haven't taken the Jeep on the highway yet with that combo, though, but we'll see how it does next week.

 

[maineiac]

i have an 89 4.0 with 4:10's and 33's and i get 8mpg

 

[Kittrell]

91 PROJECT.
3.55 with 33 1-11 miles in town and 14 highway? That is poop.
SLAYER
4.56 12-15 in town and 18-20 on the highway.
GET SOME GEARS!! heheheheheheheheehehheeheh
btw u prob have em on another one of yer rigs.

Gears, what?

 

[bobnoxious]

Combo's I've run in various personal XJ's over the years

-31's on 3.54 and auto...currently getting 17-18 MPG (yeah, I actually know how to correct for speedo error), power is fine, with no excessive downshifting.
-33's on 3.54 and auto...downshifted from OD a lot on the highway, but 3rd was a bit too much for highway speed. Never calculated mileage, but I don't remember it as being excessive.
-33's on 3.73 and auto...Same as 3.54
-30's on 3.73 and 5spd...nicely overgeared, no mileage figures, but my time/perceived distance vs. tank of gas seemed right.
-30's on 3.54 and auto...No real difference from stock, no big mileage change
-33's on 4.56 and auto...Power was good, no big mileage change after correcting for being overgeared
-35's on 4.56 and auto...still slightly overgeared (mathmatically), mileage between 15-20 depending on the off-road time and right foot
-35's on 3.54 and auto...Best highway mileage yet at 20+mpg in 3rd staying at traffic speed, around town was 10-15, power wasn't nearly as bad as everybody makes it out to be.
-33's on 4.56 and 5spd..mathmatically overgeared, mileage ranging from 15-20 depending on heaviness of right foot and amount of off-roading.

 

[bigo]

I am running 33's with 4.56 gears. I get alot better mileage with this combo then with 31's and 3.55's. I get about 20 on the road and 15 in town.

 

[iluv83vettes]

I have an 89 4.0 with the aw4, 31's and stock gears in the axles. I usually get 13mpg with a nice mix of in town and highway driving. Whenever I am on the highway I usually average 18-20. BTW the speedo is off by about 20%. I was driving down this highway with my friend behind me and I had my speedo at 75 and I was on the phone with her and I asked how fast we were going because I had never figured it since I had bigger tires and she said 90. I didn't believe her so when I got home I took my GPS with me on the highway and she was right.

 

[lawsoncl]

Don't forget to check the coolant temp sensor. Easy enough to check with an ohmmeter. If its bad, you'll run rich and get poor mileage. Might consider changing the O2 sensor if it's got lots of miles too.

For the record, I get 17 mpg with auto, 32s and 4.10 gears in my 89 MJ. It got 21 mpg when it had 3.07 gears, AX15 manual, stock tires and no lift.

 

[rocklandxjer]

no you dont, you have 33s your tires are 20% larger than the stocks, so you get around 10, unless you got a new speedo gear..., which still sucks you should check your engine, cause somethings wrong

 

[Rocketman]

ONE thing you may wanna check.

When you put on the bigger tires did you change the speedo gear on the transfer case??

The speedo gear runs your speedometer and of course, your odometer. You may actually be getting better mileage than you think.

 

[AKswampheep]

wow.. i get around 12 est city and 18 highway mpg going VERY easy on it with stock 3.55 gears and 35's.. in OD on the highway doing 60.. and the foot really light on the pedal, it pulls it along just fine.. and it still beats stock neons lol

 

[Tree Frog]

Did you change your speed O gear? If not your running faster than indicated.

 

[TheInstaller]

I do. Wierd as it may seem, the best mileage I've gotten so far in my XJ has been with 31s and stock 3.07s. I averaged almost 22 miles per gallon on my way out to Massachusetts back in July. I think in general the stock gears are way too tall, even with 225/75R15 tires. If you stop using 5th gear (or stop using overdrive 4th if you have an AW4), I expect your mileage will go up. Now I have 31s and 3.55s, and I don't use fifth. At 65 miles per hour, I'm right at 2500 RPM, which is just about perfect. I haven't taken the Jeep on the highway yet with that combo, though, but we'll see how it does next week.

I have 31's, AX-15 with stock 3.07 gears, and speedo correction. I am heading up to Vermont Saturday night, and I might just take your advice and not use 5th gear. When I put it in 5th at 65 mph, it is just a tad under 2000 rpm. Any suggestion on tire pressure for daily driving?