Gas mileage...?

What kind of mileage is everyone getting from their rigs? I did a search and found a couple threads, but one was about 'Winter Gas' (and winter air- lol) and the other wasn't helpful enough; only clue was O2 sensors.
I am only getting 10-12mpg (mixed mileage) outta my 93/4.0/242/3.55/3" lift/32" tires. I've seen some say they'r getting 18-20. WTF? I know I should be getting better mileage; I would expect to go further than 200 miles on an 18 gal tank. I will be checking my O2 sensors, but is there anything else I should look at? It is mostly stock; only engine mod is a throttle body spacer.
Any and all help will be greatly appreciated. Thx- RJ

I had the same setup (4.0/242/3.55/3" lift/32") in my 88 and got same crappy mileage.

Have you calibrated your speedo with the 32s?
If not do so. your mileage may not be all that bad.
15-20% better than you think.

Check the o2 sensor. if it has more than 50k miles on replace it.
Do a good tune up.

I regeared to 4.56's and it shot back up where it belongs 17ish when I beat on it. with a high of 21.5 all highway..

99 XJ Same set up, same mileage. If you did not recalibrate your speedometer your gas mileage will be worse. I do not see how any body could get 18 to twenty out of this set up with out serious upgrades from stock. The only thing I can see helping is to regear and that may get you back up to 14 to 16. Other things to consider roof rack, high clearance bumpers, heavy duty bumpers extra weight all add up to more wind resistance and drag. I know just by removing my roof rack with lights I gain some gas mileage. No your not alone and I imagine that most Cherokee's are the same way given the same setup. If not please post your miracle cures guys! I may buy a gas mileage car rather than try to squease more mileage from the XJ, probably cheaper in the long run.

Joe

88', 4.0, AW4, 4.11 gears, speedo is right on, 33x10.5r15 BFG At/ko's. I am getting between 17.5-20.5 on the highway. I don't check it around town because I do more highway driving. I have a K&N filter, bored TB, hi flow cat, and Borla cat back exhaust. Air comes through an ARB Snorkle. I don't have huge bumpers, just the stock stuff...took all that heavy bumpers stuff off years ago. Just put the spare in the back. I do have Thule cross bars with my Hi-Lift mounted up top but nothing to really grab the air. What it really gets down to is air, bring it in and let it out. Also I drive on the highway between 65-75 on the PA turnpike (seems I do most of my driving on it for appointments) so a lighter foot would/could help. Juice

Most likely because you still have the 3.55 gears. Bogging the engine all the time. You would probably get better milleage if you take it out of overdrive.

My 89 has a cracked exhaust manifold that makes the computer think it is lean all the time and puts in more fuel.

I get 20mpg city and about 25mpg on the highway with my '96, stock. And I don't drive like a grandma...my engine regularly sees 4000+ RPMs.


BTW - you have a 20.2 gallon tank, not 18. You will continue to get horrible mileage until you regear...

andyr354 said:

Most likely because you still have the 3.55 gears. Bogging the engine all the time. You would probably get better milleage if you take it out of overdrive.

My 89 has a cracked exhaust manifold that makes the computer think it is lean all the time and puts in more fuel.

Click to expand...

Take it out of overdrive? You can't even drive in over drive because it lugs the engine so bad. You know in and out, in and out, in and out, in and out drive to over drive. 32" and 3.55 is not a good set up but on the highway drive is the only gear you can use without eventually causing damage to your transmission.

Do the older XJ's get better mileage? Mine is 99 and I never got over 18 and most of the time 16 even with a fresh tune at 30,000 miles? I drive it very nicely on the road! I just can not belive any one could get over 20 on a consistant bases. These things are about as aerodynamic as a brick. Oh but I still love it.

ZmOx, how do you account for that excellent gas mileage? What kind of gas do you use? Any additives? Does it ever noticeably vary--AC season, pre-tuneup, different gas? You mean your car is absolutely stock--no non-OEM aftermarket parts?

I don't have an accurate reading on my '96 yet, being on just my 3rd tank of gas, but I'd sure like to think I could attain that kind of MPG.

ZmOz again: and what size are your tires?

ZmOz said:

I get 20mpg city and about 25mpg on the highway with my '96, stock. And I don't drive like a grandma...my engine regularly sees 4000+ RPMs.


BTW - you have a 20.2 gallon tank, not 18. You will continue to get horrible mileage until you regear...

Click to expand...

I've asked you about this before on another board and I just don't understand how a '96 can get 25 mpg. The 20 mpg in the city is also hard for me to comprehend to since my xj drinks gas around town--like 13-14 mpg. The best I ever got was 21 mpg and I think thats pretty darn good considering the epa figures are only 19 mpg on the hwy. Your '96 is OBDII and slighly more efficient than my '95, but the EPA figures on yours are only 20 mpg on the hwy. MY XJ is tip top too, I recently gave it a full tune up, all the vacuum lines and ccv stuff replaced, I had the engine professionally flushed, and the fuel injectors cleaned, the cooling system is all new and was recently flushed, and it was very well maintained before I got it and it just turned over 90K so its fairly low mileage. The only gas I ever run in it is Chevron and BP. I also have a K&N drop in and a new high flow cat and Flowmaster 50 series delta flow and my XJ has the stock suspension and I'm only running 225/75/15s on it. It did come with 225/70s, so my speedo is off a hair, but not enough to make a notable difference in gas mileage. The exhaust is new, so it might get 22 mpg or so, but there's no way it'll ever see 25 MPG. My mom's pos CRV gets 25 mpg, but its a 4 banger cuteute. Idk, through all of this my XJ runs great, but it didn't really effect my gas mileage very much. You also stated that you engine regularly sees 4000 rpms plus and that kills my gas mileage when I run it hard. Is there some secret that I don't know about, are you sure you are figuring your mileage correctly?

I really can't explain it. Yes, I am measuring correctly. My GPS agrees completely with my odometer. It's got almost 200,000 miles on it too. 225/75/15 tires, the only modifications so far are a few holes I drilled in the air box and a partially bored TB. (I was boring the lip on the bottom out myself, but my bit broke so I just stopped half way though) It was only getting 11mpg, until I replaced the ORIGINAL spark plugs/cap/rotor/wires/fuel filter. The last time I went on the highway I was going up to mount hood - 170 mile round trip, with 3 200lb+ men, 2 dogs, windows down (more drag), and several miles of it going up a mountain in 3rd gear. Got a little over 24mpg. And since then it has warmed up, and I have filled the diffs and transfer case with synthetic, so I wouldn't be surprised if I saw 26mpg. And yeah, I give it alot of gas when I go, as my friend says I "drive like a crazy bitch". :looser:

I can't explain it, but I'm certainly not complaining. :spin1:

I wouldn't complain either. I still don't get it though.

It must be those holes in the airbox. What's an airbox & why would you drill holes in it? And precisely how big a hole did you make in the TB before your drill broke? You might have stumbled onto something really big.

My tires are almost new (5K mi) Michelin XCX APT 30 X 9.5. The previous owner put them on because he thought them safer on Maine winter roads (it was his wife's commute car). How many mpg do they cost me? Do you think they are really safer than stock size tires? If so I certainly don't want to change them; I've had 3 bad accidents on ice/snow. If not I hate to give up gas mileage for nothing at current gas prices. And I don't much like the rubbing on sharp turns.

30x9.5 won't do much too your gas mileage. They're not much bigger than stock. I was getting the good mileage before the holes in the air box and bored TB.... If you're looking for more mileage the best thing to do would be to put synthetic in the transfer case and differentials. You could easily get 2+mpg.

I don't think drilling holes in the airbox would make that big of a difference. If it did, taking out the restrictor airhorn from my intake would improve my gas mileage and I haven't noticed any increase in my gas mileage since I did it last fall.

how do you check your O2 censors, where are they and how do oyu know when to replace, i get shitty gas milage, its horrible, i got stock gearing and 6 inch w/33 swamped on my xj. i know the tires of course bring the mpg down alot with stock gearing. how do you recalibrate your speedometer aswell? thanks

I just had the transmission fluid drained/replaced & I assume they did the same to the diff./transfer case? I'm planning to switch to synth at my next oil change coming up in another 1000 miles. We have an outstanding quick-lube-type place in Brunswick. Can they switch the diff/Xfer case when they switch the engine oil?

Thanks for your--& everyone else's--patience w/my ignorance. I'm crazy about my little red truck & want to be able to drive it til the end of my driving days & then give it to a grandchild. (They're all peagreen w/envy.)

my 1990 gas milage sucks and I an rolling stock, I get 12-18, depending on my mood. I kind of miss my 1987 yoda 2wd that got 30 mpg damn gas prices, 2.19 at arco even!!!!!!!!!!!!!!!!!

Specs of my XJ are below but when I run my 235 road tires the speedo is pretty much right on. Driving at about 60-65 (I think that the older XJ's like mine are geared to driving at 55) I get from 20-22MPG. Rebuilt motor about 30k ago too so that helps some. In town mileage varies according to how hard I flog it.

Thanks for the input, guys. Though I can hardly believe my eyes (wish my smileys worked here), even 12-15mpg would be acceptable, IMO- but 18-22/25 ??? Unbelievable. (Damn broken smileys)
And if I gotta 20gal tank (never got more than 18.something in it), I'm getting 10 mpg if I'm lucky. Of course this is with the oversized tires/incorrect speedo; I will do a search on correcting the speedo next thing. (Damn broken smileys)
In the meantime; does anyone know the math to convert my 200 miles into the correct distance traveled with 32" tires? (I'm not even sure I asked that right.)(Damn broken smileys) Or to figure my actual mileage per gal?
Thanks for the help- RJ