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Old 02-23-2011, 05:40 PM   #1
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Really BAD MPG, Need help please!!!!!!

Okay guys, i have been reading alot and i have the feeling my jeep isn't performing properly. My MPG is very horrible it's 13 - 14 MPG, when it should be atleast.... 16. (Today i filled it up and received 10 mpg) I have 31 inch tires, very heavy bumper with a windch i would saw weighs around 3 - 4 hundred pounds. I also don't drive fast max 60 mph. I drive normal only a couple times I speed. on streets i'm always driving 35 mph in 3rd gear and i don't use 5th gear. I have a flowmaster series 44 muffler, and the muffler piping ends right under neith the passenger side seat. I don't have the piping that extends to the rear. Also it's a 4.0L High output recent oil change, engine has 223k miles, recently tuned engine, and rebuilt tranny. gears should be the regular best performance one, i believe 3.57 or something close to this.

Question - What type of gas should I use? 87, 89, 91? Chevron, Shell, Arco?

Question - What type of spark plugs?

Question - What can i do to have the best fuel economy for my jeep? Recommendations please be specific, like brown gas kit what is that?

Question - Is it possible the additive they put into the gas for winter is hurting my jeep?

I really want to improve my fuel economy, i'm a student I drive at least 20 miles per day. and selling my jeep is not an option. By the way. I saw a drastic change when i installed the muffler / new 02 sensor. before i got 250 per fill up and now i'm barely getting 200.

Please any suggestions I need help!!!

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Old 02-23-2011, 05:49 PM   #2
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I have an 06 LJ - stock. I get 10 mpg in town and 16 on the highway.

Q1 - 87 octane
Q2 - Doesn't matter much
Q3 - Light on the skinny pedal, proper air pressure in tires, proper maintenance - thats about it
Q4 - Yes...its also not uncommon to see fuel economy drop in the winter as a result of longer warmup times (even driving right away still has the engine in a cold start mode - dumping more fuel in than is needed once warmed up).

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Old 02-23-2011, 06:05 PM   #3
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I have an 06 LJ - stock. I get 10 mpg in town and 16 on the highway.

Q1 - 87 octane
Q2 - Doesn't matter much
Q3 - Light on the skinny pedal, proper air pressure in tires, proper maintenance - thats about it
Q4 - Yes...its also not uncommon to see fuel economy drop in the winter as a result of longer warmup times (even driving right away still has the engine in a cold start mode - dumping more fuel in than is needed once warmed up).

Thank you, also have you seen a difference between Arco (reg gas) Chevron (techron gas) and shell (nitrogen v power gas)? Does any of this stuff really help??
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Old 02-23-2011, 07:34 PM   #4
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Between my bike and Cutlass, both of which require premium, and my Jeep, which always gets the lowest grade available...I've never once noticed a difference from one gas station to the next. My vehicles get the same mileage whether I fill up at Shell, Phillips 66, BP, or the mom and pop station thats only open til 8 PM...

I know some people claim to notice a difference between certain stations...but I never have. So I choose gas based on convenience...
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Old 02-23-2011, 07:43 PM   #5
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Having same problem. Getting about 14.2 miles per gallon and it's driving me nuts. Just replaces fuel filter, plugs, and new fluids in everything. Someone or everyone give us the inside scoop.
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Old 02-23-2011, 07:47 PM   #6
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Your exhaust could be hurting your MPG. You changed a system that was specifically designed for your vehicle with proper backpressure. Try putting the old one back on for a tank or 2 if possible and see if that helps. If it does you need to decide if the "better" sound is worth the worse MPG.
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Old 02-23-2011, 07:54 PM   #7
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Rolling resistance has a lot to do with it if you have bearings that are worn or needing new ujoints or other stuff like that it could affect it. Easier it is to turn stuff the more mpg/power you will have but not by much
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Old 02-23-2011, 08:06 PM   #8
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Quote:
Originally Posted by Bubba68CS View Post
I have an 06 LJ - stock. I get 10 mpg in town and 16 on the highway.

Q1 - 87 octane
Q2 - Doesn't matter much
Q3 - Light on the skinny pedal, proper air pressure in tires, proper maintenance - thats about it
Q4 - Yes...its also not uncommon to see fuel economy drop in the winter as a result of longer warmup times (even driving right away still has the engine in a cold start mode - dumping more fuel in than is needed once warmed up).

I have a 2000 4.0 with about the same milage as stated ^ running on 31x10.50. The 16 mpg is flat ground with no wind!! Jeeps have the aerodynamics of a brick.
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Old 02-23-2011, 08:49 PM   #9
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i have a stock 95 jeep and i get about 15 idk whats going on i done a full tune up.
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Old 02-23-2011, 08:57 PM   #10
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Well I do run 33x12.50x15 on it with the 2.5 lift but I should be getting maybe 15.5 max
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Old 02-23-2011, 09:25 PM   #11
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Throgh E-10 into the mix and theres the real problem.
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Old 02-24-2011, 02:34 AM   #12
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I would use 5th gear when you can. I can get 16mpg average can get better if I try. My little 2.5 runs great at 40-45 in 5th. Also do the trick to add 5 gal to your tank. I can run 300+ on a tanks
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Old 02-24-2011, 03:52 AM   #13
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Seafoam. Stuff is amazing at de-gumming anything. Put the crap in your tank for 2 or 3 fill ups and if that doesn't work put the same stuff in your oil, wait a week or go and change your oil. It'll descale and clear out the varnish buildup wherever the oil can reach. Mines a 92 and I've just been using it at each fill up and oil change and the mpg went from 13-17 in 4 tanks of gas. Also the ghetto way to do it is to strip down your car when it's not too cold and make it into a rolling gas can (strip out back seat, top, winch, doors... You get the idea)
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Old 02-24-2011, 05:48 AM   #14
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My Stock 89 Carbed 4.2 gets 16-20 MPG depending on whether it is Winter or Summer, whether I have the hard top on and which way the wind was blowing. But I am running P245s with no lift as a DD. I can use 5th no problem from 35MPH up to 85 mph.

I once had a cop try to give me a ticket. He said I was doing 89 and pulling away. For the record the fastest I have seen it is 87 downhill with a tail wind. I am pretty sure that was terminal velocity.
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Old 02-24-2011, 05:53 AM   #15
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I seem to get 13.5 with 33s 4 inch lift and 4:56 gears
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Old 02-24-2011, 06:19 AM   #16
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13-14 is what my 97 4.0 gets if I drive it easy.
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Old 02-24-2011, 07:52 AM   #17
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Why do you say you should get 16 ?
Curious
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Old 02-26-2011, 02:06 PM   #18
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Why do you say you should get 16 ?
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From.what I have read I should be.getting better mpg. I don't drive in 4wd, I drive slow accelerate slow. Today I went to extend my piping from muffler to the end of the car near gas tank do you guys think this will help with backpressure? Maybe I don't have enough and im just wasting fuel?
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Old 02-26-2011, 04:48 PM   #19
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You drive 35 in 3rd. And don't use 5th, I don't know how you expect to get better gas mileage.
I'm doing 35 with 4th gear and anything 45 plus in 5th and I get 16-18, 20 on rare occasions.

The only things i think you could do is reduce you tire size and drop some weight like the winch the big heavy bumper, if you have a hard top switch to the soft top. remove all the seats except the drivers seat.

You will get worse mileage in the winter which is normal, part of it is the extra load of the Heater, the longer warm up times before driving, the gas mix might have something to do with that too. Hard to say.
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Old 03-01-2011, 01:23 PM   #20
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you are lucky to be getting that MPG. At 7200 feet, with the crappy BBD carb and a glasspack on headers, with 31x15x10.5 tires i am lucky to pull over 10. if i never leave town i will get 13. i can feel the wind resistance start at 45 and we always have wind!! 5th gear? what is that? oh yeah, i did get to use it as soon as i dropped down below 5000 feet LOL!! every modification you do to increase power and or lift will reduce the MPGs. good luck
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Old 03-01-2011, 01:37 PM   #21
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95 4" lift 33x12.50x15 dura trac side exhaust intake spacer 3.73 gears and i get 15 in the wisconsin winter we drove from wi to logan utah and hwy speeds we got 19......... its the cold..... your jeep is running fine, my lexus rx300 went from 21 to 15-17 mpg because of the cold...... just keep a record and see what happens when it warms up!!
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Old 03-01-2011, 03:02 PM   #22
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mine gets like 10 totally stock with 29s. need to do a tune up.
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Old 03-02-2011, 02:20 AM   #23
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Well so far i haven't filled up the tank yet, but i have less sound, i can feel more high end power. I'm pretty sure that by me adding the exhaust from mid car to rear end it did help a little. I'll inform after I do my initial fill up. Like i said before, i only go to school, so i don't drive everywhere (thank GOD)!!! loll

Alright guys, i'll ttyl thanks for all the inquiries, i appreciate it!
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Old 03-03-2011, 02:55 PM   #24
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its a jeep. not mpg. fpg. fun per gallon. lucky to see 12mpg on mine.4.0 5 speed 3.07 gears and 33x12.50 tires.
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Old 03-03-2011, 04:39 PM   #25
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Like!!!
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Old 03-16-2011, 06:21 PM   #26
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its a jeep. not mpg. fpg. fun per gallon. lucky to see 12mpg on mine.4.0 5 speed 3.07 gears and 33x12.50 tires.

Ha! I used to say it gets the most SMILES per gallon
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Old 03-16-2011, 07:37 PM   #27
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I bought my jeep cause my 2500hd was sucks down the fuel haha
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Old 03-16-2011, 11:19 PM   #28
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i get 18mpg with 4.0L 33x12.5r15 with a total of 5" lift standard tranny, i don't have any extra weight like a winch or upgraded bumpers. Because of the oversize tires, my speed isn't accurate which makes my odometer inaccurate... I drove my wife's minivan 1 mile and marked it. Then took my jeep and drove the same distance and found that the jeep was .2 miles less then what the van reported. So (some math here) I take my total trip mileage and multiply it by .2 than add that number to my trip mileage then divide that by gallons added and get my MPG.
Looks like this: 201miles (according to trip mileage) X .2 (the offset) = 40.2miles then 40.2 + 201 = 241.2 actual mileage. If it took 11gallons to fill it up... 241.2 divided by 11 = 21.92 MPG This is just an example... I don't 22 mpg, but I do get 18+/-. Then I do the math at that MPG and multiply that by the 20 gallons in the tank and then mulitple that number by .8 add that number to the first number and that is the total mileage I can go on one full tank of gas... whew... and if you followed that, you are my hero, I may have gotten lost there.,.
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Old 03-16-2011, 11:33 PM   #29
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i get 18mpg with 4.0L 33x12.5r15 with a total of 5" lift standard tranny, .,.
Why the heck do I get 10mpg then...... I have the same setup i wish I knew how to get better mileage I've done so much! I think
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Old 03-16-2011, 11:50 PM   #30
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c.m. I am grateful i get the mileage I do... I don't know what I do different... I do know that i tried to drive it conservatively and got worse mileage...

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