I have no lift, no bumpers, no roof rack, no excessive weight on my car at all and I am getting around 15 mpg!! I changed my spark plugs, went to a sythentic blend oil and new oil filter. I dont know why my gas mileage is so bad. the only mod i did is new wheels and tires (stock) any body have this problem or have any suggestion to fix it!!

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2002 Jeep KJ Sport 3.7L 4x4

245/75-16 Mastercraft Courser HSX, 16x7 Cragar, 2" OME MD Lift, ARB Bumper
AEM Brute Force Cold Air Intake, Flowmaster Super 44 Muffler

Currently working on: Full service on transmission & bed-lining ARB bumper

viewtopic.php?f=43&t=84650

Go easy with the right foot on the skinny pedal. Oh, and let off the skinny pedal as soon as you know that you know you need to slow or stop - it will coast a great distance.

Most KJ's do not get much more than that. (I SAID MOST! Those that disagree, nobody wants to hear that you get 87mpg so save it! )

The best way I have found to increase MPG is to drive easy with no hard acceleration and coast when coming to a stop.

The more you mod the worse it gets...

Later,
J

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[size=9]Used to have a 2002 Steel Blue Limited
LOST #000462

Not really enough info. Has this always been your mileage? Is this based on your own calculations or based on the KJ computer? Did it change with the new tires? I don't remember what stock tire size is, so did you put larger tires on? If so did you have the computer reset?

Switching tires can reduce mileage if you've gone to a sticky tire for better grip.

Gas can play a huge role. I filled up out of town and immediatly lost 5mpg, dropped from 18+mpg down to 13ish.

I'll assume that you're not looking at the computer in metric mode. If you're looking at the KJ computer the algorithm is biased towards mileage at the beginning of the trip.

this is based on my own calculation (not very accurate??) it bought the firestone destination a/t tires (235/70r16). I usually try to go the speed limit.

edit - anyone know where the fuel filter is located - looking to replace it. aftermarket replacements??

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2002 Jeep KJ Sport 3.7L 4x4

245/75-16 Mastercraft Courser HSX, 16x7 Cragar, 2" OME MD Lift, ARB Bumper
AEM Brute Force Cold Air Intake, Flowmaster Super 44 Muffler

Currently working on: Full service on transmission & bed-lining ARB bumper

viewtopic.php?f=43&t=84650

He did say that the replacement tires were stock size...

If the fuel filter were bad, I would guess that it would cause a lean condition and cause th ecomputer to throw a code.

The speed you drive is not as impartant as how fast you get to that speed. If you are even a mildly agressive driver (even if you do the speed limit) you will see a large difference in MPG.


Later,
J

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[size=9]Used to have a 2002 Steel Blue Limited
LOST #000462

I went 40,000 before any mods except the K&N - that brought it to 18-20, back before the lift, and tires, and roof rack and boulder bars...... - now I'm back at the 15 I was when it was new.

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2002 KJ, Stone White, 4WD, Off Road Group, Selec Trac, Trac Lock, Fuel/Transfer/Tran Skid Plates, Tow Group. Spider rock guard, K&N filter, 2.5 lift, roof rack and boulder bars by All J Products. L.O.S.T. #000091 and LOSTKJWEST member.

My Liberty says to use 87 grade gas. Before I read that I used 85, the grade I see everyone use in town. My gas mileage was 14 in town, 18 on highway at that time, but I use 87 now and I average 20. The lowest I see it go is 17 these days. BTW, I am completely stock, still!

If the fuel filter were clogged up bad enough, your milage would really drop and it would more than likely run like pure crap. I get 14-15 myself. I thought not running the a/c would get me some better milage, but running it actually has little to no effect (.1-.2mpg less) so i've stopped suffering through the heat....lol.

KJean, is that a drop in K&N you put in? If it got you that good results i'd be willing to try it.

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--Tim

-LOST #005816
-2003 KJ Sport
-3.7L V6
-235/70/16 Bridgestone Dueler A/T REVO'S
-Factory Fogs
-Sunroof
-Custom Mounted Mag Lite
-Jeep Stainless Steel Coffee Mug
-Autozone Rubber Floor Mats

Fuel filter is a life time filter and not intended to be replaced. It is on top of the gas tank. If you need to replace it drill out the rivets of two of the tie downs in the back (don't remember if its the ones toward front or rear of KJ - think its was the rear). Pull up the carpet to expose a trap door. Remove the bolts and break the seal and pull this up. The filter should be right there.

85 Octane?? Does Dollar General have gas stations where you're from? Seriously, isn't 87 normally the 'regular' grade? 89 Mid-grade and 92 or so Premium?

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Adam,
2005 Liberty Renegade
Locked & Lifted! Rusty's Coil & Powertrax NoSlip, 245/75/16 Bridgestone Dueler MTs,
CB w/ 4' Firestick mounted on Tire Carrier,
Full MOPAR Skids, RRO Diff guard, 'AllJ Boulder Bars, Rhino-lining applied to sides.
On-board Air (Superflow MV-50)

I was thinking the same thing!

Later,
J

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[size=9]Used to have a 2002 Steel Blue Limited
LOST #000462

In the northern half of Utah, regular is 85, premium varies from 87 to 91. Something to do with higher elevation?

I've always used 85 and noticed no difference when I tried 87 for a while, but I didn't really track MPG very closely.

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09 Yellow JK Rubicon LOST #TY050608
TeraFlex 4" long arm lift, 35" BFG KO2s, Tatton driveshaft, Riddler diff covers, RIPP headers,
MBRP off road exhaust, Cobra C75WXST, Little Passengers 3rd row seat
Formerly: 02 White Ltd 4x4 with lots of stuff...
Pics: http://troysterr.com Links & Parts: http://youngs.org/kjparts

Here in Farmington, Northwestern New Mexico, regular grade gas is 86 Octane. Seems like an altitude thing. I saw that a lot of gas in Utah or Colorado is 85, but if I head out to Arizona along the Colorado River(less than 1000 feet above sea level), or Death Valley(Sea Level or below), then 87 Octane is the norm.

Jeep recommends 87 Octane, and even specifies NOT putting anything higher in. Here, mid grade is 88, and premium is 90.... What a quandary!

Are you using the computer to figure the fuel economy? I have "heard tell" of programming/software upgrades for the Liberty that might improve things. Or maybe disconnect the battery over night and let the computer reset itself?

I can personally verify that the computer can have a lot to do with fuel mileage. Since I had mine re-programmed for the larger tires, my fuel economy has been creeping upward. Prior to re-program, I was getting around 15.5 average combined city/highway. After the re-program, the city mileage crept up to 15.9 average. I took about a 350 mile road trip yesterday, and the average jumped up to 16.5. That means the highway fuel mileage was considerable higher to bring up the average . Shifting was a lot smoother and there was less of it also.

I understand that your Liberty has stock tires. I am just suggesting that perhaps a "reset" might help by giving the computer a chance to "start over" learning your driving style...which may help, (or may not).

I've had to disconnect my battery a few times for various reasons, and every time I'm surprised by the change in performance afterwards. Usually the engine just seems to run smoother and accellerate better. Lasts for a day or two. I haven't monitored MPG very closely, but at least one time it seemed to go down slightly.

I don't think you have to disconnect it overnight. An hour or so should be plenty.

Not something you want to do often, though, if you don't like resetting the presets on your radio.

I don't have any expert knowledge on this...just reporting my observations. Would be interesting to hear from someone that actually knows what they're talking about.

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09 Yellow JK Rubicon LOST #TY050608
TeraFlex 4" long arm lift, 35" BFG KO2s, Tatton driveshaft, Riddler diff covers, RIPP headers,
MBRP off road exhaust, Cobra C75WXST, Little Passengers 3rd row seat
Formerly: 02 White Ltd 4x4 with lots of stuff...
Pics: http://troysterr.com Links & Parts: http://youngs.org/kjparts

Yep, I had the same type in a neon and it added a LOT of mileage there also.

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2002 KJ, Stone White, 4WD, Off Road Group, Selec Trac, Trac Lock, Fuel/Transfer/Tran Skid Plates, Tow Group. Spider rock guard, K&N filter, 2.5 lift, roof rack and boulder bars by All J Products. L.O.S.T. #000091 and LOSTKJWEST member.

Did some googling on the net and came up with some basic information on octane vs. altitude. got this from the autoreviewonline.com site:

" A car that requires premium gasoline at sea level will probably run equally well on regular gasoline at high elevations — 5,000 feet or above. The reason is that, as altitude increases, the car's octane requirements are lessened due to the change in the air/fuel mixture. Thinner air at higher elevations means a richer air/fuel ratio, so less octane is needed to fire the cylinders.

That's why, in the areas you note, which are at higher elevations, the regular gas is only 85 octane: Vehicles simply don't need as much octane to give comparable performance because of the thinner air and consequent richer air/fuel mixture.

This same factor explains why the computers in many new cars are programmed to make altitude-specific adjustments to the engine's air/fuel ratio. "

FWIW, I just got back from a trip from Phoenix (1200 ft) to Albuquerque (5000 ft). Regular unleaded down here in PHX is 87 oct, up in ABQ it is 86. My milage over the trip (900 miles) was around 22-22.5. The most important thing I can say is be easy on acceleration and use the cruise control whenever possible. I used to have a BMW R850R bike that I initially ran 91 oct. in until I realized that the 86 oct. worked just fine. I even tried 100 oct. once and got some of the worse milage on the bike

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Kevin
AD5VG
Just another red Jeep in the world...
L.O.S.T. #KB051963

the low grade gas here in Montana is 85 octane. I also just took a trip to Topeka, Kansas and got 18mpg from here to Denver, then 21 mpg all the way across to Topeka. On the way back, i only got between 14 and 15 mpg, but i was pulling a 65 Rustang on a car dolly. with the a/c on. it did great pulling, no significant speed loss unless it was a big incline. I do find the cruise control a little annoying, it waits too long to shift down one gear, so when it does it shifts down two, and so it doesn't hold the same speed very well if you are going through rolling hills. i also figured out that if you are installing a hitch and trailer wiring, do the wiring harness first, then put the receiver hitch on. If you put the hitch on first, it's hard to get the harness snapped into the holes in the floorpan above the hitch.

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'04 Renegade
Many mods on,
Many mods to come.