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  #1  
Old January 2nd, 2009, 13:04
walkerja191 walkerja191 is offline
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Why is my gas mileage so bad

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?
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  #2  
Old January 2nd, 2009, 14:09
90Pioneer 90Pioneer is offline
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Re: Why is my gas mileage so bad

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.
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  #3  
Old January 2nd, 2009, 14:17
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MnGrnXJ MnGrnXJ is offline
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Re: Why is my gas mileage so bad

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?
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  #4  
Old January 2nd, 2009, 15:13
igotanxj igotanxj is offline
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Re: Why is my gas mileage so bad

Quote:
Originally Posted by thisisme19 View Post
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?
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  #5  
Old January 2nd, 2009, 16:37
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winterbeater winterbeater is offline
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Re: Why is my gas mileage so bad

13 MPG on short trips around town in the winter and warming it up a little would be totally normal.
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  #6  
Old January 2nd, 2009, 16:43
igotanxj igotanxj is offline
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Re: Why is my gas mileage so bad

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Originally Posted by winterbeater View Post
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.
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  #7  
Old January 2nd, 2009, 17:17
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winterbeater winterbeater is offline
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Re: Why is my gas mileage so bad

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?
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  #8  
Old January 2nd, 2009, 17:20
Jeepm@n Jeepm@n is offline
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Re: Why is my gas mileage so bad

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.
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  #9  
Old January 2nd, 2009, 17:34
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badandy badandy is offline
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Re: Why is my gas mileage so bad

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!
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  #10  
Old January 2nd, 2009, 17:39
igotanxj igotanxj is offline
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Re: Why is my gas mileage so bad

Quote:
Originally Posted by winterbeater View Post
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.
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  #11  
Old January 2nd, 2009, 18:07
xcm xcm is offline
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Re: Why is my gas mileage so bad

Quote:
Originally Posted by Jeepm@n View Post
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
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  #12  
Old January 3rd, 2009, 00:29
Monkey55 Monkey55 is offline
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Re: Why is my gas mileage so bad

Quote:
Originally Posted by igotanxj View Post
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
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  #13  
Old January 3rd, 2009, 04:30
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Hammered Hammered is offline
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Re: Why is my gas mileage so bad

Quote:
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

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  #14  
Old January 3rd, 2009, 13:23
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Mtb Jak Mtb Jak is offline
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Re: Why is my gas mileage so bad

winter gas effects it too..
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  #15  
Old January 3rd, 2009, 14:02
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time2getdirty time2getdirty is offline
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Re: Why is my gas mileage so bad

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

Last edited by time2getdirty; January 3rd, 2009 at 14:05.
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