REALLY BAD FUEL ECONOMY

[BillDunn83]

you are never going to get "good" gas milage with a modified XJ. you may be able to do a few theings and gain a mile or 2 to the gallon but you will not be able to get an astronomical improvement without going back to stock IMO. even stock these things were lucky to get 20 mpg.

 

[Voteban]

you are never going to get "good" gas milage with a modified XJ. you may be able to do a few theings and gain a mile or 2 to the gallon but you will not be able to get an astronomical improvement without going back to stock IMO. even stock these things were lucky to get 20 mpg.

I agree with this. That's one reason that I have my motorcycle that gets 70-80mpg :thumbup:

 

[Darky]

Specs:

00' With stock bumpers / body and a Con Ferr roofrack with my spare up there and 4 Hella 500FFs.
4.5" Lift with 32s
Stock Gearing
AW4 / 242

Offroad in 4WD Low -- 7-10mpg
Around town in Full-Time 4WD (Weather) -- 10-12mpg
Around town in 2WD -- 12-16mpg

I have some sea-foam that I'm going to run through the engine soon and do an oil change with new spark plugs and hopefully I'll see some of these numbers go up. The roofrack surprisingly doesn't feel like it adds any drag, you're already driving a toaster. :rof:

Your stock gears are hurting mileage and I bet you'd see an improvement if you took the roof rack off. Regearing will likely get you the biggest improvement though.

you are never going to get "good" gas milage with a modified XJ. you may be able to do a few theings and gain a mile or 2 to the gallon but you will not be able to get an astronomical improvement without going back to stock IMO. even stock these things were lucky to get 20 mpg.

Stock, I averaged 20, got up to 22 highway, on 235s. 3/1.5" boost with 30s, I average 18 on stock gears. As it sits now (in sig) I get 12...

 

[jeeptech1]

mechanics stand point. first off disconnecting the battery to relearn the pcm will do nothing, dont do it. most newer xjs only have the fuel filter as part of the pump (no external filter). the roof rack is not hurting anything, i had one on one of my jeeps and my mileage never changed. taking it to a shop and having the fuel system professionaly flushed could help, but hard to say. o2 sensor, possible but that new of a jeep watches it so close that it would be throwing a code. change your plugs. try unplugging your programmer and see what happens (more power=more gas). i dont see how having 31's on stock gears is killing it. it should technicaly get a little better as installing bigger tires(within reason) effectively lowers rpms on the freeway. i had a wrangler on 31's with 3.07s that got 17 on the freeway. start with the plugs and unplugging the programmer and as someone else said, keep your foot out of it!

 

[cueball767]

Upgrade your coil. Splurge for a quality intake and header. Those will make a noticable difference.

 

[TRCM]

This may sound unlikely, as yours is so new, but make sure you TC is locking up.

On mine, I was getting the same mpg as you, and I determined my TC was NOT locking up. I put in a switch to allow me to force it to lock up, and my mpg jumped back up to 16 on the highway.

 

[bert01xj]

are you basing your miles on the speedo if so that is not showing the miles you have traveled and you gas milage is a little better then that.

 

[magimerlin]

X2. Have you corrected your speedo yet? Also agree about if you do not take trips all the time that require the roof rack take it off and put back on when needed. The spare tire hanging off the back will hurt mileage to as far as weight is concerned. Leave th spare at home if just going about regular day to day stuff. Get AAA just in case if you want. It's cheaper per year then the gas that is spent by always having that extra 100+\- pounds of dead weight hanging off the rear bumper. And a good tune up never hurts either.

 

[tigmeister]

X2. Have you corrected your speedo yet? Also agree about if you do not take trips all the time that require the roof rack take it off and put back on when needed. The spare tire hanging off the back will hurt mileage to as far as weight is concerned. Leave th spare at home if just going about regular day to day stuff. Get AAA just in case if you want. It's cheaper per year then the gas that is spent by always having that extra 100+\- pounds of dead weight hanging off the rear bumper. And a good tune up never hurts either.

Really? You may want to put your spare inside for aerodynamics and yes not having it saves weight, but how much time are you gonna waste waiting for AAA to get there and fix a flat when you could be back on the road in 5 minutes? The more weight you can remove, the more it will help your mileage. I don't leave any "essential" equipment behind, no matter what it's going to cost me in mileage, period!

 

[DrMoab]

You have an 01. Get used to crappy fuel mileage. I've tried every trick in the book to get better fuel mileage and nothing works.

Last year when we went to Colorado I went the extra mile to gain fuel mileage. I dropped the roof rack, pulled the manual fan and installed an extra electric one, pulled the front driveshaft and pumped the tires up to 40 lbs. even driving like a grandma at 60-65 for the entire 450 mile trip my mileage went from 13 up to about 14. Not enough for all the extra work I did.

 

[Talyn]

They are on the passenger side frame rail, kinda near the right rear tire.

Not on the return less fuel system (which his 2000 has). Its in the tank.

 

[cheapcherokee93]

regearing should net you the best gains, nothing else you can do to counteract all that extra weight and the bigger tires. as been said, 4.56 would probably be the best bet for you, you can't gear a jeep too low, heck maybe even consider 4.88s ?

for those telling him to get a better coil or upgrade the wires, the 01 has a coil on plug system therefor there are no wires and the coils are not upgradeable.

 

[Tim_MN]

The root cause of your low mpg's is a faulty O2 sensor (or a cracked exhaust manifold on 1999 and older). If you have a 30-40% drop in mpg's, you need to look at the O2 sensors (and/or mainfold).

With 5.5" lift, 3.55 gears, and 31's, I get 14-16 city and 16-18.5 hwy. Stock it got 20 mpg hwy.

You are adjusting you odometer readings (and thus your mpg's) for the over-sized tires, right ? You also need to allow for a 10% drop due to winter blend gasoline.

Regearing, a clean roof, injector cleaner, new plugs, reduced weight load, staying under 70mph, each will add a few 10th's to your mpg's.

 

[91to99]

I don't think the OP will see your responses. This thread is over a year old and the OP hasn't been on since then. LOL

Roof rack never hurt mpgs in my 91 w/31s and 4:10s.

 

[Jeep450r]

Just run in 3rd gear on the freeway

Edit: jk old thread

 

[cheapcherokee93]

I don't think the OP will see your responses. This thread is over a year old and the OP hasn't been on since then. LOL

Roof rack never hurt mpgs in my 91 w/31s and 4:10s.

oh man, i didn't even realize that. :laugh2:

i blame cueball767 for resurrecting it :eyes:

:twak: