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MPG down the tubes...

JeepXJ93

JeepXJ93

NAXJA Forum User
Location
CT
2000 xj w/ 88k on it. Bought the jeep a few months ago and got about 260 miles to a tank of gas before the warning light would come on...installed an RE 3.5" SF kit and 31's on it, wheeled about once a week(small trails about 45 min to go through) noticed my gas mileage was crap. And to this day is only getting worse...i went from one week 260 miles till the light came on to the next week, 200 miles till the light came on...then the week after that which was this past week, i barely hit 200 w/ the light being on for 20 of those miles....right now i need to head to a gas station b/c i'm that close and i only have 120 miles on the tank...used 4wd for about 4 hours due to the snow storm....i didnt think that should decrease my mileage by 140miles to the tank though....just put new champion truck plugs in thinking my originals were shot but i havnt noticed any diff....what should i do? Thanks for any thoughts/info.

P.S...the same kid that i went wheeling w/ the same amt. of time...had a wrangler, but still got around 260 on a normal week, dropped to about 240, but no where near my pathetic 120
 
This is probably pretty obvious, and you may have already checked, but I'll mention it anyway...

Could you have punctured your fuel tank or lines or such during your light wheelin? It is possible that you are leaking fuel and the leak has been getting worse in the last few weeks due to a myriad of things...weather, more wheeling, etc.

Even light wheelin had the potential for damage.

Just a thought!
 
Sounds like a combination of problems.

31" tires with stock gears will reduce your MPG by about 3-5.
The lift ads weight and increases air drag (yer sittin up further) 1-2 mpg
Extreme cold will reduce MPG another 2-4
4X4 on the road another 2-4
snow can also take a big bite out of mileage depending how deep, but lets just be really conservative and say another 2 mpg's for 1" of snow.

add it up and that's 10-17 MPG's less than ideal. So going from 230 miles to 120 miles per tank is about 11 MPG reduction.

I say you're doing OK, for now. If it keeps up when the weather moderates then you need to look at other things like brake drag, drive train alignment and boring stuff like that.
 
yea, i just got it aligned about a week ago, but havnt noticed any increase....so my buddy has a 98 wrangler w/ 31's on it and stock gears....my old 93 had a rusty's 3" lift w/ the same 31's i have now...the wrangler gets 260 and my old 93 got at least 200...i figured less b/c obviously the tank size but also b/c its older w/ more miles and wear on it. Anyways, i checked for leaks, not thoroughly but i didnt smell any gas anywhere...no dents in my tank or anything like that. Also the snow here in CT never got past 3 inches on the roads i was traveling on. And i was pretty much paired up w/ two other jeeps (both running 31's and stock gears) and they still got the normal mileage maybe 1 or 2 mpgs less. Only reason i'm thinking its not the snow or anything like that is b/c the first week i had the lift on i lost about 65 miles from one tank....and there was no use of 4x4 that week, accept off road for about an hour. I guess i'll just keep an eye on it. Thanks
 
When you fill up get a receipt form the pump and write the odometer down on the back, and store them in a bag in the center console. That way you can accurately keep track on the mileage over time.
 
Did you change out the speedo gear when you went to bigger tires?
Jeep on!
--PEte
 
What do these things get on average anyway? I have a '95 2WD (hangs head in shame) with Rancho 2" BB and 31" BFG ATs with stock (3.07) gears. Mileage is around 15-16 MPG, but is usually better in the summer. A friend had a '90 XJ-style Wagoneer and got at least that, but his was 4WD.
 
no i didnt change the speedo gear.....i didnt on my 93 either and never noticed this big of a difference....my buddy w/ the tj also didnt change his w/ 31s and he didnt notice any kind of significant drop either.
 
john mitchell said:
Sounds like a combination of problems.

31" tires with stock gears will reduce your MPG by about 3-5.
The lift ads weight and increases air drag (yer sittin up further) 1-2 mpg
Extreme cold will reduce MPG another 2-4
4X4 on the road another 2-4
snow can also take a big bite out of mileage depending how deep, but lets just be really conservative and say another 2 mpg's for 1" of snow.

add it up and that's 10-17 MPG's less than ideal. So going from 230 miles to 120 miles per tank is about 11 MPG reduction.

I say you're doing OK, for now. If it keeps up when the weather moderates then you need to look at other things like brake drag, drive train alignment and boring stuff like that.
Click to expand...
.............................

Thank you for that. My mileage has gone from 17-18 last spring & summer to 13-15 this winter & that's after new O2 sensors, full tuneup, switch to synthetic, brake job. I keep my tires aired, I have the world's lightest accelerator foot & I was getting really discouraged until I consulted NAXJA and read about the winter fuel additives that reduce MPG. That eased my mind a little and your list of other contributing factors makes sense. I have 30" tires, there's been slush on my roads for weeks now & I've been in 4W HI most of the time, and the temp has ranged from -8 to +17 since Christmas.

If it doesn't get noticeably better as the weather improves I'll have the man who did my brake job check for drag. That's the only thing I can think of to do. Which reminds me of a question I asked several weeks ago on a thread that died before I got an answer (maybe because it was such a dumb question): are some 02 sensors more accurate than others? Could a bad one possibly affect gas mileage?
 
Maybe this is already accounted for, but I did not see it specifically mentioned.
You went up in tire size, to 31" from stock size?
If the speedo gear was not changed, then the spedometer reading as well as the mileage on the odometer/trip meter are not properly calibrated.
Could this be it?
 
I would definitly check to see if your speedo is correct first. I found that mine was off before the lift & 31's, and now is right. If you never see any of those portable speed desplays in you area you might ask your local speed trap atendee to assest you. I get in the high teens with mine with mostly city driving. Lastnight I was playing in the snow in low range and was surprised at how much gas I used.
 
If you want to validate speedos to see how far non-stock wheels may have skewed things, use someone's handheld GPS to verify your speed and odometer error.

It's a Useful Thing to have around a Jeep anyway...

-sc
 
My '98 XJ is set up just about like yours. I get right at 240 miles before the fuel light comes on UNTIL I put my full-size spare on top which cuts it down to 200.

The easiest way I've found to check your speedo is to watch mile markers on your next long drive. Get a full tank and drive 100 miles according to the mile markers. If your odometer doesn't match the 100 mile mark, that is the mileage difference and the percentage difference that your speedo is probably off.

My odometer reads right at 94 miles when I pass the 100 mile marker. Means the speedo/odometer on my '98 XJ reads slow by 6% but yours may differ. (I don't consider a 6% difference significant.)
 
I'm in a similar position after having just put on a set of 31's...I did however out of curiousity clock every trip I made with my GPS for a couple of days and discovered that for every 14-15 miles I clocked on the GPS my odometer was approximately a mile behind. So where you were getting 260 or so on stock tires, the 31's would cut approximately 17-20 miles off your odometer and give the appearence of huge drop in your gas mileage.

Then add in as everyone has been saying the winter fuel mixture, and your mileage is deffinitely going to drop.

Matt
 
Winter in the Northeast = Oxygenated gas and and average of a 75 miles less per tank with a 4.0L. Nothing really you can do, just wait for spring.

--Matt
 
don't feel bad, i just went on a road trip this weekend, avg mpg 12.67. that is on the hwy fully loaded (4 passengers, gear for the weekend) 87xj 6" lift longarms, 4.56's 33x12.50's
 
don't mean to sound like a simpleton, but here goes.

I have a stock 93 xj and my light started coming on sooner and sooner.
Turns out I am not using anymore gas...really.
I fill up and drive 200 miles on a tank. Then fill up again.....only I am not on empty as my low fuel indicator would have me to believe. I still have over 1/4 tank.
So it is actully my fuel sending unit....not worse mileage.

just my .02 worth.
 
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