Why is my gas mileage so bad

[walkerja191]

I have a '94 Cherokee sport 4.0 with a 4 inch lift. I have tiny tires on it right now for the winter and I am only getting 13 mpg. Does anyone have any idea what could cause this?

[90Pioneer]

I would say you're damn lucky.

My 96 XJ, when stock, would only get 12MPG no matter what I did!!

Now heavily modified and weighted down w/ lots of steel, it gets 10mpg.

[MnGrnXJ]

Thats some crappy gas mileage... Check your air filter, plugs, wires and coil. I just did a tune up on my 96 XJ and replaced all of 'em and I am getting 20 on the highway and 17 in city. Of course my Jeep is totally stock at the moment so that prolly makes a bit of a difference.

oh yea, when was the last time you changed your o2 sensors?

[igotanxj]

Originally Posted by thisisme19

Thats some crappy gas mileage... Check your air filter, plugs, wires and coil. I just did a tune up on my 96 XJ and replaced all of 'em and I am getting 20 on the highway and 17 in city. Of course my Jeep is totally stock at the moment so that prolly makes a bit of a difference.

oh yea, when was the last time you changed your o2 sensors?

X2

My 96 gets 20mpg on the highway with 2" boost and 29s. Check all the above mentioned stuff expecially your upstream O2. If it's original- replace it. A lifted XJ will get worse mileage, but I don't think it should get that bad. Also, what is "tiny" tires?

[winterbeater]

13 MPG on short trips around town in the winter and warming it up a little would be totally normal.

[igotanxj]

Originally Posted by winterbeater

13 MPG on short trips around town in the winter and warming it up a little would be totally normal.

Thats true, if you do a lot of around town driving, and lots of short trips where the engine is basically just trying to warm up the whole time, then 13mpg would be normal. Highway is a different story tho.

[winterbeater]

Just tested my stock 2000. Slightly disapointed at 18 MPG at sustained (3 hour) 80MPH drive. I expected about 20. I did have a 5 or 10 minute warm-up included in that though, but I think that's just an excuse. This vehicle is new to me and I probably need to test the O2 sensors. Should bad O2's show up with a code reader?

[Jeepm@n]

I just read in OEM tech that a gentleman had a loose connection on his temp sensor causing his Jeep to stay in open loop mode. Not allowing the engine to use the O2 sensor to adjust air fuel ratio. My 96 and my 94 average around 17-18 in the winter months. All backroads and 30% 4wd use.

[badandy]

I've noticed a drop in fuel mileage in all three of my vehicles, '07 Buick Terraza, '06 Chevy Van1500, and '92 XJ

Here in Florida it's been attributed to E-10 being added at the pump:

http://www.floridajeepers.net/viewto...hlight=ethanol

If you read through the entire thread some have noticed as much as 23% loss in power as well as a loss in mpg!

[igotanxj]

Originally Posted by winterbeater

Just tested my stock 2000. Slightly disapointed at 18 MPG at sustained (3 hour) 80MPH drive. I expected about 20. I did have a 5 or 10 minute warm-up included in that though, but I think that's just an excuse. This vehicle is new to me and I probably need to test the O2 sensors. Should bad O2's show up with a code reader?

I would say that's because of the 80mph speed. Slow down to 60-65mph (i know, it sucks) and you'll get your fuel economy back. XJ's have the aerodynamics of a brick. If your O2 sensors were bad you'd be getting closer to 10-13mpg. Usually, they don't show up with a code, but if you can read live data, a bad O2 sensor might read lean.

[xcm]

Originally Posted by Jeepm@n

I just read in OEM tech that a gentleman had a loose connection on his temp sensor causing his Jeep to stay in open loop mode. Not allowing the engine to use the O2 sensor to adjust air fuel ratio.

i dunno about HO's, but on a renix, a missing, or wrong thermostat will have the same effect. if you havent been into the cooling system, this is a high probability on 15+ year old cars bought for cheap. i have found at least 3 xj's were missing the tstat while working on them.

when was last tune-up?.
o2 change?
cat-change? could be plugged

[Monkey55]

Originally Posted by igotanxj

I would say that's because of the 80mph speed. Slow down to 60-65mph (i know, it sucks) and you'll get your fuel economy back. XJ's have the aerodynamics of a brick. If your O2 sensors were bad you'd be getting closer to 10-13mpg. Usually, they don't show up with a code, but if you can read live data, a bad O2 sensor might read lean.

I agree.

18mpg at 80mph is pretty good..

winter - no need to test the O2 sensor based on the mpg at that speed.

E

[Hammered]

I am only getting 13 mpg. Does anyone have any idea what could cause this?

keep in mind youre driving cinder block on wheels. Heres what I got, not sure if you want to throw money at this stuff.

http://www.performancedistributors.com/jeep.htm

[Mtb Jak]

winter gas effects it too..

[time2getdirty]

i have a 98 with 5" of lift 31" tires 4:10 gears and im getting 21 mpg!