If it makes you feel any better ...
My Power Wagon gets 11 in the city, 11 on the highway, 11 on the beach, 11 towing another truck down the beach ... it's pretty much always 11.

 

I have a 99 xj,4.5" lift, 33x12.50s and get 14 cit,16high. Stock everything. Its all in driver and where your at. Alot of $ to swap gears to gain a few mpg. Stick to what you got.

 

Ok guys, figured I would bump this thread to ask a new question. I'm probably going to be changing the upstream O2 sensor sometime this week, hopefully that helps my mileage.

What things would cause bad gas mileage without throwing a code?

 

Poor driving habits, probably...

 

i have 4.5 inch lift 5 speed with 32's and im getting 14-16mpg i mean different years so i don't know if that will have anything to do with it?

 

3.55 gears with 32" tires is the problem. Without regearing you will not see much of an improvement. I know, because I am contemplating getting 33x10.5x15 on stock gears for a bit until I can swap them to 4.56s. In the mean time, bad MPGs.

 

No. I drive mostly highway, and am EXTREMELY light on the throttle.

The 5 speed might make a small difference, because i believe the gears are different. Maybe that was just 4cyl that the gears were different though? I can't remember.

I understand that gears affect mileage, however they shouldn't be THIS bad.

A 5-6 MPG difference is too much, which is what is making me think there is something wrong.

 

Tell you what... try driving around in 3rd for the entire next tank full and see if you mileage improves.

It's getting frustrating when we keep telling you what your problems probably are but you don't want to listen, insisting that something else is wrong. Change your spark plugs, air filter, fuel filter, clean your injectors, check your tire pressure, roll your windows up, replace all of your engine sensors... but what ever you do, don't regear or put in the correct speedo gear- that might just prove we're right.

 

Here's the problem i have, how is it possible that some people can get 15-16 MPG with the EXACT same set-up as me, yet i can only get 10-11 almost all highway. That's why i'm trying to hint that there might be something wrong.

If it's frustrating you, i've got a great idea...don't read/post in this thread. Seems like a pretty simple concept to me .

 

I get 11 MPG with with XJ and it has 30x9.5 at the moment with a 3.5" RE Lift, so I have it worse lol.

I figured the horrible mileage should be the exhaust manifold with cracks in it, have you checked that?

 

have you ever adjusted your Trans kick down cable... Just curious... Someone told me that this could cause bad gas mileage but i am not sure that this is true...? I figured I would throw this out there....

 

I have a 99 on a 6.5 lift and 33s. Everything else is stock. I drive all highway and used to get right around 300 miles to a tank of fuel. Now Im lucky to get 160 mile to a tank. PUT GEARS IN IT.

 

If you have an AW4 and you're running stock gears with 32" tires driving around in 3rd instead of overdrive should improve your mpg. If you're in OD you will not be in the "power band" of the motor when driving normal and this will cause you to push harder on the gas pedal than necessary- spending more fuel. In 3rd you will be at a higher RPM and even though you'll be reving the motor higher it will spend less fuel. It's sort of the same effect as changing gears. After lifting my '92 (running the same size tires and stock gears as you) I never used OD again. Drove it for 4 years that way and now the new owner drives it that way too with no ill effects. I recommended this out of all seriousness, trying to still help.

There are lots of things that can effect mpg. Just a few small hills in your 15% of non-highway miles can make a big difference compared to someone else that lives in an area where there are no hills at all (like Florida), so you're bound to see some differences. I see a lot of people getting the same mpg as you though, so maybe they live in a comparable terrain as you. Outside tempature, type of gas you use, condition of your battery, and the list of things that can cause poor mpg goes on. I know if I drive my car one mile to the highway and then stay on the highway until i need gas again I can get 3 to 4 mpg better than if I am doing 15% around town and the rest on highway.

So driving around in 3rd will not hurt anything, and if you live in an area that has hills I can bet that your mpg will improve. Let's try it and see if you notice a difference.

 

i get 10mpg 33 12.5 15 92 xj auto stock 3.55's
all new sensors, real good running motor. These 4.0's suck down fuel

 

I have a 1998 xj with a 4.5 inch rc lift and 32s I was gettin a little over 300 per tank now I'm lucky to get 250 I haven't really added it all up to get to actual mpgs but it is a big differnece from stock to lifted. And xjs aren't at all the most aerodynamic vehicle so lifting them just put more wind drag on them