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OK Uncle, I need to improve mileage or sell the Jeep.

A

Angus

NAXJA Forum User
Location
Kansas City suburb
After much thought and many dollars for gas I need to do something. I don't want to sell the XJ but I need to improve the mileage. I've got a 4.0, AW4, 4.11 gears, 32x11.50 BFG AT's and 5" of lift. I started lifting from day one, 2000, and do not know what my mileage should be. I do know that currently it gets 12-14mpg depending on if I turn it off at every stop light and do not drive over 60. I cannot lower it to stock since I have a WJ converted front end and steering, but I can go to 2". With the 4.11's, 30" or 31" street type tires and 2" lift what mpg might be possible? Just thinking out load while crying.

Angus
 
I hate to be "That guy", but this has been covered over and over again.


The usual questions turn up:
Are you accounting for the different gears and tires?
Manual or automatic?
4WD or 2WD?
Mostly City, or Hwy use?
What weight oil are you using? Engine? Axles?
What kind of Fuel are you using?
What pressures are you running you tires at?

How do you drive:
Are you aggressive, or do you relax and let traffic do it's thing? How do you come off lights?


I think the 4:11's are too deep for 32's, but that's a gut feeling. For the best Hwy miles, since you have an engine that has bottom end torque, you want to take advantage of that. Did you change your Speedo gear, or calculate a factor for your tires/gears?

Auto's generally get a tad less gas mileage than a Manual.

Extensive City use tends to drag down the MPG figures.

Heavy, high viscosity oils have more drag than low viscosity oils. 5-30W for regular oil, or even lower if Synthetic are EPA "gas saving" oils.

Running low pressures on the street is a sure fire way of getting low mileage.

Lastly, how you drive will have a large affect on your mileage. Jack-Rabbit starts, stop and go traffic, and driving aggressively will waste fuel.
Relax, don't be in a hurry, use a lower gear in "creeping" traffic to crawl along at idle just enough to plod along behind the guy infront of you.
Accelerate smoothly from a stop, and decelerate smoothly from Speed.
 
Zuki-Ron said:
I hate to be "That guy", but this has been covered over and over again.


The usual questions turn up:
Are you accounting for the different gears and tires?
Manual or automatic?
4WD or 2WD?
Mostly City, or Hwy use?
What weight oil are you using? Engine? Axles?
What kind of Fuel are you using?
What pressures are you running you tires at?

How do you drive:
Are you aggressive, or do you relax and let traffic do it's thing? How do you come off lights?


I think the 4:11's are too deep for 32's, but that's a gut feeling. For the best Hwy miles, since you have an engine that has bottom end torque, you want to take advantage of that. Did you change your Speedo gear, or calculate a factor for your tires/gears?

Auto's generally get a tad less gas mileage than a Manual.

Extensive City use tends to drag down the MPG figures.

Heavy, high viscosity oils have more drag than low viscosity oils. 5-30W for regular oil, or even lower if Synthetic are EPA "gas saving" oils.

Running low pressures on the street is a sure fire way of getting low mileage.

Lastly, how you drive will have a large affect on your mileage. Jack-Rabbit starts, stop and go traffic, and driving aggressively will waste fuel.
Relax, don't be in a hurry, use a lower gear in "creeping" traffic to crawl along at idle just enough to plod along behind the guy infront of you.
Accelerate smoothly from a stop, and decelerate smoothly from Speed.
Click to expand...

well said! make sure your ignition,fuel system (including filters) are up to notch and oxygen sensors do not last forever! whens the last time you've replaced it?
 
OK, I guess I need to be more specific, but I thought I said most of the needed info. 2000 XJ with a 4.0 and AW4 automatic, 8.25 rear, D30 front with synthetic gear, t-case and motor oil (Mobile one 5-30). Trans is DexIII dino as per factory recomendation. Tires are actualy overinflated for my rig to help mileage. I do not drive the car over 60 highway and the engine slowly revs to no more than 2000rpm in town.

I have searched without luck to my exact situation. I am wondering what my change in mileage might be in removing the lift. I put on the first lift and tires after 150 miles, 8 years and 115000 miles ago. I guess I'm also looking for moral support. I am an experienced mechanic that knows most of the tricks, but am not having much luck with my XJ. If you know a better search word let me know please, otherwise be a bud and let me know your opinion or experience.

Thanks guys, Angus
 
OK again, the O2 sensers are 15,000 miles old and work well. I am very particular with my vehicles as I also work on Firetrucks. I own a diagnostic scanner and all sensors and readings show good. My only question may be the injectors, but it is for my peice of mind not that there is any indication they are bad or dirty.
 
gasket matching the manifolds with the head might help a little, along with polishing the intake. I'm not sure how substantial a gain it would produce, but every little bit helps
 
The sad truth is, lifted Jeeps aren't going to get good or even great mpg. Most everyone I know has the Jeep as a toy and the DD is a little econobox.
 
Markw, that is the point of my whole post? I realize the lift and tires are hurting the mileage. I was only wondering how much of a improvement I might expect if I drop everything and retire. Is 2-3 mpg out of line?


Oh and to one of the others, the speedo has been corrected and is acurate.
 
I only get 15-16 in mine, maybe 19-20 on the highway and it is basically identical to yours minus the lift and tires. I have found that I do get slightly better mileage if I accelerate quicker, about half throttle and let it rev out to 3500 or so. I've verified this with my Scangauge.

The horrible mileage is that "Jeep thing" you always hear people talking about.
 
15-16 city and 19-20 highway would be huge for me! Do you have 4.10 gears also?
 
Straight open highway driving (road trip) mileage for mine is near 20...thats with 4.56 and 35's. Also with 5.5 inches of lift. Around town I have gotten as bad as 12...heavy foot :D

I would say you should be getting better. I would expect a gain of about 3 mpg across the board if you drop to 2 inches and 31's. Also...go with a narrow tire. A 31x9.50 will get better mileage than a 31x12.50. Take off the rack and cb antannas if you have them. Lighten the load too...minimize the tools, parts, etc that you carry day to day.
 
Angus said:
15-16 city and 19-20 highway would be huge for me! Do you have 4.10 gears also?
Click to expand...

Oops, I missed that part of your first post... My gears are stock. I do have a few engine mods, AEM Intake, Pacesetter Header, Dynomax exhaust and I've raised the back of my hood a 1/2" to help keep the heat out. I didn't notice any change in mileage with any of those mods except the hood.

I do think having my Scangauge(it's mounted on my steering column) helps considerably with my mileage. Always knowing exactly what mileage I'm getting really changed my driving habits.

You never did answer if you were compensating on your mileage figures for the tires and gears, or if your speedo has been corrected.
 
MisterFubar said:
Oops, I missed that part of your first post... My gears are stock. I do have a few engine mods, AEM Intake, Pacesetter Header, Dynomax exhaust and I've raised the back of my hood a 1/2" to help keep the heat out. I didn't notice any change in mileage with any of those mods except the hood.

I do think having my Scangauge(it's mounted on my steering column) helps considerably with my mileage. Always knowing exactly what mileage I'm getting really changed my driving habits.

You never did answer if you were compensating on your mileage figures for the tires and gears, or if your speedo has been corrected.
Click to expand...

He sure did look at post #9 last line its ok we forgive you.
 
Well, I have a 90 with 4.0 and auto, running ~5.5" lift, 33's and fullwidths. Running 3.50 gearing, and drove it to Moab from northern Minnesota averaging 19 mpg (got as high as 23 in the mountains). For me the key was keeping it out of overdrive to keep the revs in the sweet spot of 2000-2500 rpm.
 
Angus said:
OK, I guess I need to be more specific, but I thought I said most of the needed info. 2000 XJ with a 4.0 and AW4 automatic, 8.25 rear, D30 front with synthetic gear, t-case and motor oil (Mobile one 5-30). Trans is DexIII dino as per factory recomendation. Tires are actualy overinflated for my rig to help mileage. I do not drive the car over 60 highway and the engine slowly revs to no more than 2000rpm in town.

I have searched without luck to my exact situation. I am wondering what my change in mileage might be in removing the lift. I put on the first lift and tires after 150 miles, 8 years and 115000 miles ago. I guess I'm also looking for moral support. I am an experienced mechanic that knows most of the tricks, but am not having much luck with my XJ. If you know a better search word let me know please, otherwise be a bud and let me know your opinion or experience.

Thanks guys, Angus
Click to expand...

Given those rpms its impossible youre getting 12mpg... how EXACTLY did oyu calculate your mpgs?
 
Angus, do you have a roof rack? I get 15 around town with 33s an stock gears.. Auto with lite foot.. Useing gps for mileage..Mine is a 89
 
With 265 LT and 3.55 gears behind a 5 speed I have seen 26 MPG at 60 MPH. In a 01 with 35k on the clock. (near) Stock does help and a fresh but well broken in engine make a big difference.
How many miles on your clock?
Park the XJ and get fire and theft on her. Get a 4 banger
 
Last edited:
My heep gets 13-15mpg. I noticed that the fuels with 10% ethonol gave me the worst mileage. Now I will go out of my way for the pure gas!
 
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