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  1. #1
    Join Date
    Jun 2016
    City/State
    Toronto, Ontario
    LJ Year
    2005
    Posts
    10

    extremely poor gas mileage 2005 LJ

    Hi everyone, I own a 2005 jeep unlimited LJ, 6 cyl. auto, 31 inch tires, the problem I'm having is extremely poor gas mileage. I get 150 kms per tank in the city and close to 200 on hwy. I know it should be better, but it's not. I'm in Toronto, Canada, and was wondering what kinda gas mileage you get? Is there any things I can replace/repair to get a bit more mileage? When starting from a stop it revs up to @2300 rpm before it shifts. is that not high? I use reg. gas, and add fuel injector cleaner in a full tank. Had a tune up, still the same. I'm wondering if the transmission is shifting too high, but nothing showing on a garage computer. I have even changed gas caps too. Anyone have any suggestions?

  2. #2
    Join Date
    Aug 2012
    City/State
    Highland, IL
    LJ Year
    2006
    Year Purchased
    2012
    Posts
    159

    Re: extremely poor gas mileage 2005 LJ

    2300 RPM is not high for the 4.0. You could check some of your numbers on this gear calculator. Maybe a PO has changed the diff.gears?
    http://www.grimmjeeper.com/gears.html

  3. #3
    Join Date
    Aug 2012
    City/State
    Highland, IL
    LJ Year
    2006
    Year Purchased
    2012
    Posts
    159

    Re: extremely poor gas mileage 2005 LJ

    I didn't do the math. What's your MPG?

  4. #4
    Join Date
    Jan 2015
    City/State
    Les Escoumins, Qc
    LJ Year
    2005
    Posts
    86

    Re: extremely poor gas mileage 2005 LJ

    A lot to per mile! Wow

    Now assumi g that a full tank of gas is about 68 litres, that puts you way up theire at 34 l per 100 kms. Wow! By the way, the only way you can calaculate your fuel efficiency is miles to the gallon of litres per hundred km. Just milage w/o the gas quantity means nothing.

    Now that would be about 6.8 miles / us gallons.

    Again, all based on a full fill up of 68 litres or about 18 us gallons.

  5. #5
    Join Date
    Jun 2016
    City/State
    Toronto, Ontario
    LJ Year
    2005
    Posts
    10

    Re: extremely poor gas mileage 2005 LJ

    Hey, Sounds bad, 34 to 100 km....My tank is a 72 litre tank, the low fuel light comes on, then I fill up it takes 50 litres. so it's basically a 50 litre tank. 22 litres still in tank, I can't afford to run outta gas here. Either or, 150 kms divided by 50 is still around 3. 3 kms per litre. My 04 jeep tj manuel trans gets me 300 city, 400 hwy. But I should be getting a bit better then that in my lj. I will check out the gear ratio, it could be possible the PO changed it, converting 34 liters per 100 kms is 6.92 gallons

  6. #6
    Join Date
    Jan 2015
    City/State
    Les Escoumins, Qc
    LJ Year
    2005
    Posts
    86

    Re: extremely poor gas mileage 2005 LJ

    Quote Originally Posted by rock2004 View Post
    ......, converting 34 liters per 100 kms is 6.92 gallons
    Us forum = US gallons. They are smaller than imperial the one we use north of the line.

  7. #7
    Join Date
    Jan 2015
    City/State
    Les Escoumins, Qc
    LJ Year
    2005
    Posts
    86

    Re: extremely poor gas mileage 2005 LJ

    So at 50 litres to 200 km that gives you 25. No good, but not as bad.

    Question, waht kind of driver are you? Do you floor it and go fast from light to light or chug along?

    You did not mentionned it, but I would check the basic, like air filter, spark plugs, I also wonder if cat could not be plug.

    You mentioned your rpm, but what is it at cruising speed, like 100kph and at your regular driving speed and what is your driving speed? Real one with gps if you can, just in case the ratio are were changed by P/O.

    And it is winter, so if really cold, milagge will be worst if really cold, Na forget about that you are in Toront do not think you get much -20 C and less.

  8. #8
    Join Date
    Jun 2016
    City/State
    Toronto, Ontario
    LJ Year
    2005
    Posts
    10

    Re: extremely poor gas mileage 2005 LJ

    Hey Lucky J, thanks for replying to my posts. I try to stay under the 2000 rpm range, as I heard that helps. I'm a slow driver from start to finish.LOL..I did the basics, air filter, spark plugs, ran it thru computer all sensors are good. At 100 kph it runs at 2000 rpm. I tried to post a pic, but it didnt work on this site. Yes it is cold up here, so I drive my 04 tj to work and back. I drive the LJ in the summer. I thought maybe the tires were dragging it down, really like this jeep, so roomy and very sharp looking, but i need better mileage. what kinda gas mileage do you get in yours?

  9. #9
    Join Date
    Jan 2015
    City/State
    Les Escoumins, Qc
    LJ Year
    2005
    Posts
    86

    Re: extremely poor gas mileage 2005 LJ

    I will say between 15 and 17 / 100 km, but I am often heavier that I should be.

    Most of the time drivem with 33"x12.5" with the original 3,73, front and rear winch, heavy rear bumper /tire carrier with room for two 5gal jerry can plus a rear drawer set-up for gear and ARB fridge.

    Add on top of that an off road trailer on every long trip.

    But I'm not heavy right foot. Just bearly above limit. And it is a manual.

    Of course, with the trailer fuel consomption is higher than that.

    No realy good other idea bit tire pressure, brake drag and load. I'm trying to remember if they have an other cat that does not have sensor just before mufler? If so, could it be plug? I'm a little mix-up here after spending 20 year with my YJ, the LJ is only 2 years old for me,

  10. #10
    Join Date
    Jun 2010
    City/State
    Dexter, MI
    LJ Year
    2005
    Year Purchased
    2005
    Posts
    382

    Re: extremely poor gas mileage 2005 LJ

    The biggest question is what tires did your Jeep have stock and if the gears in the differentials have been changed.

    Your speedometer and odometer are off by the same percentage difference between the circumference of your stock tires and the circumference of your 31s. You need to allow for that when you calculate your mileage (and your speed). A bigger tire makes the Jeep go farther on one revolution than a stock tire and your speedo/odo are based on the RPM a sensor sees on the back of your transfer case. It's set to the stock gearing and tire size, so as soon as one/both the tire size and/or gearing changes, computer/dash see the wrong vehicle speed for that RPM.

    You can do the actual math calculations between the circumference of the current tire and the stock tire to "correct" your odometer readings or you can use your phone and a speedometer app to see what your displayed vs. actual speed is. Calculate the percentage difference between the two sizes or speeds and apply that to your odometer and keep it in mind for your speed. Your stock tire size is on the sticker just inside the drivers door on the tub. If you don't know what gears you have in the differentials, there's a couple ways to find out, a google search will probably find a number of videos showing how.

    Used to be that you could change a gear in the tcase to correct for this error in older Jeeps, but in the 05 it's an electronic sensor. BlueMonkey Motorsports makes a plug-in unit I have used on mine to correct both the odometer and speedometer for any tire/gear combo. I actually need to update it for the 5.13s.

    I reviewed it here:
    http://currentissue.jpfreek.com/publ...ver=html5&p=24

    With all that said, you should be able to get more than 170 miles/300 km or so per tank even when built. I'm on 37s with an intake/header/exhaust and just went to 5.13 gears in my 05 and I just got 190 miles on my last tank (maybe 16 gallons, I don't specifically recall) with mostly city/rural driving.

    Do not try to keep the engine below 2000 RPM, that's part of your problem, you're "lugging" the engine by keeping it well below its power band. The 4.0L can run 3000 RPM all day long and high speed cruising should be around 2750-2800 or so. The 4.0 is happiest between 2-3000 RPM.
    Project LJPFreek
    '05 Rubicon - original owner
    GR8TOPS Safari Cab & Exogate | Mishimoto radiator | JKS JSPEC 3" lift & ACOS Pro front spacers | BDS belly up skid | 1" Daystar BL | 37" Interco IROK NDs on Bird Dog wheels | OR-FAB Bumpers | WARN 10-S Platinum winch | 3" PIAA LEDs | Poison Spyder steering box skid, JCR sliders | 5.13 gears & Nitro Xtreme diff covers | ORO U-turn Steering |Kleinn OBA

    http://currentissue.jpfreek.com | http://www.jpfreek.com

  11. #11
    Join Date
    Jun 2016
    City/State
    Toronto, Ontario
    LJ Year
    2005
    Posts
    10

    Re: extremely poor gas mileage 2005 LJ

    Hi guys . I went to the dealer today, and they said that my lj has 3.73 gears. it had 30 x 9.50x 15 tires from stock. I have 31 x 10.50 x15 on it now. I did the grimmjeeper calc. it come up with 3.85 gears rounded it up to 4.10s. Do you think I'm lugging the motor by trying to stay under 2000 rpms while driving? Causing more fuel consumption?

  12. #12
    Join Date
    Jan 2015
    City/State
    Les Escoumins, Qc
    LJ Year
    2005
    Posts
    86

    Re: extremely poor gas mileage 2005 LJ

    You either have 3,73 or 4,10 or more or less, but no in between.

    So yep, under 2000 at higwhay speed on 31's could be a little hard on the engine. But perso, I do not think that they are that happy at 3 000 or above for extend periodes of time. But again, you have the auto.

    And also, what you have right now is prety on the fuel consumption. So If all the mechanical is up-to date, I would start experimenting on varius rpm. But only so much you can get on that side to.

  13. #13
    Join Date
    Aug 2012
    City/State
    Highland, IL
    LJ Year
    2006
    Year Purchased
    2012
    Posts
    159

    Re: extremely poor gas mileage 2005 LJ

    I agree with keeping it above 2000. I would like to be 2200 to 2500, but need to regear. Automatic OD sucks. Nobody said anything about going over 3000.

  14. #14
    Join Date
    Jun 2016
    City/State
    Toronto, Ontario
    LJ Year
    2005
    Posts
    10

    Re: extremely poor gas mileage 2005 LJ

    I have notice with od off it seems to move easier, while driving in city, but on hwy I switch on and rpms will drop, I think I have to get used to switching od off when driving city. I am going to get the blue monkey plug in, that should help I think, also will check that sensor on cat, if there is one. maybe the cat is shot too. Maybe I'm expecting something that isn't gonna happen, and gotta live with the ****ty mileage. I'll let you guys know what happens, I have learned so much from you guys already, thank you for the help. L

  15. #15
    Join Date
    Aug 2016
    City/State
    Black forest, Germany
    LJ Year
    2005
    Posts
    5

    Re: extremely poor gas mileage 2005 LJ

    Hi LJ-Friends, the 3.73 gears with the 31" tires is not the best, but its ok. How many km/mls are in your LJ?

    First Check what you can do on your own. The right tire pressure, clean air Filter, enough oil......check your sparks aswell. In my opinion you have got a Bad co sensor. Your lj has got 4 of them. The 2 on the top side of the exhaust are for the right mixture of air and gas, the 2 in front of the cat are only to check what comes thru your exaust.

    Take the LJ to the garage or shop you trust. They can check these sensors by obd.

    If one or both Sensors from the top are gone, only take oem, not bosch!

    Oh man, my english is a little bit rusty, nur i think everybody understood what i mean? Many greetings from oversea and good luck

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