I'm geting craping gas milage and don't know why I am any ideas

 

Yeah, youre probably running an ethanol mixture! lol, just kidding.

Our Jeeps are NOTORIOUS for getting poor mileage. When is the last time you had a tune up? Cap, button, wires, plugs, filter, oil change, trany fluid, etc. Do you have a roof rack that catches air? Drag will cause your mpg's to go down. How about a fuel filter? Do you run bigger tires? There are TONS of variables in calculating mpg's. Give her a good, thorough tune up and youre likely to see a gain. Also, buy GOOD fuel! There is a local convenient store in town that Id rather buy my fuel from to support them. However, whenever I do and I get on the highway, my Jeep sputters like crazy. She HATES the cheapo gas.

 

More details.... has this been happening through several tanks of gas over several thousand miles? Just the last tank of gas? If it has just been the last tank or so it could be bad gas. If you have already filled up at another location and same results it could still be bad gas from previous fill up. Go get some premium gas treatment and add it to your tank and hit 60+ for about 10 miles. If you have already tried this and same result then I don't know what to do from there. Worked for me before.

 

Also any recent mods? Lift? Tires? Change in altitude? Change in octane? You should run the 85 octane if it is available in your area. XJs love it.

 

Also, if youve added weight (you, girlfriend, bumper, etc.) that will lower your mpg's.

And to add to the 85 statement, I once put premium in mine and I attribute it to blowing a sensor. It was the fuel sensor on/near the throttle body (cant remember the exact name of it). We filled up and they were out of regular, so I used premium. An hour later on the highway it starts sputtering. Not to bad at first, then REALLY bad. Then the engine light came on. If I hadnt been near my exit I dont think I would have made it. It couldve been a coincidence for sure, but it was an odd coincidence.

 

I have heard that O2 sensors can go out and cause bad mileage, just something to consider.

 

1. Tuneup hardware MUST be fresh.

2. You must have at least 3 samples before coming to any conclusions.

3. Those samples must be obtained by math. Miles driven divided by gallons consumed

4. Need to know if this is city driving, highway, or combined

5. Any check engine light? If so, codes must be retrieved for guidance

6. How old are your oxygen sensors?

 

Is an oxygen sensor something that should be changed regularly, i.e., every "X" amount of miles? Ive owned my '99 since '02 and never changed it (that I can remember). I was always under the assumption that they didnt need changing unless they went.

 

Alright guys there are no mods but I am running 31s and I have done a fresh full tune up already and motor/ tranny fluids I have a little tool boxes in the back and it's been like this for awhile since I've owned it I've put more than 5000 miles on it only geting 12 miles to the gallon and the tune up was all done like right after I got it and seen I was geting bad gas milage and I do know that not having overdrive doesn't help but I still shouldn't be get that bad of gas milage out of it I've done everythang I could think of before making this thread

 

I dont know what else to tell you. Mine doesnt get a whole lot better than yours (never has since I bought it 3 years old with 40K on it), and its pretty much stock and maintained well (tune-ups, etc.) Lots and lots of variables. Alignment OK? If its not running funny, throwing codes, check engine light, etc., then I dont think you have an issue, just an XJ. Gas is still MUCH cheaper than a car payment, unless you drive an hour or more to work every day.

 

Haha ya I'm 16 and tryen to get a little better gas milage haha
Xj's for life haha

 

Did you regear with them larger tires?
if not, your actually getting bout 15-16 mpg

 

I know the feeling. My first car was a '71 Cutlass 455 Rocket and got like 7 mpg. Gas was only a buck, but it cost me like $20 to fill it and I didnt get very far on a tank. Hated that car with a passion and sold it for scrap for $50. Not a day goes by that I dont regret doing that.

 

check the front and rear dif fluid too. If it hasnt been changed in a long long time, that could be a part of it.

 

Sounds 100% normal. My 93 has had a FULL tune up. oxygen sensor, tps, plugs, wires, cap, rotor, fuel filter, air filter, and every oil replaced with synthetic except the transmission, and i swapped in 703 injectors.

I averaged anywhere from 12 to 15 mpg with 31's. Probably the same or slightly less now..