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Old 02-04-2014, 02:21 PM   #1
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2.5L bad MPG

Hello, I have a 92 jeep with my MPG averaging me at about 8 at the moment with no ideas as to why at the moment... just wondering if anybody could point me in a direction to start looking but at this time I have tried or replaced everything I can think of

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Old 02-04-2014, 02:35 PM   #2
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O2 sensor?

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Old 02-04-2014, 02:37 PM   #3
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I can tell you that I get horrible mileage as well. Anywhere from 10-11mpg.

I have:
2.5L
33" Tires
Stock gear ratio
AX-15 (Upgraded)

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Old 02-04-2014, 02:39 PM   #4
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O2 sensor replaced, all tune up parts done (plugs, cap, rotor, coil fuel filter), air filter cleaned, MAP sensor replaced, CTS replaced, throttle body has been cleaned, fresh fluids everywhere (not that that should cause a huge issue)
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Old 02-04-2014, 02:55 PM   #5
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O2 sensor replaced, all tune up parts done (plugs, cap, rotor, coil fuel filter), air filter cleaned, MAP sensor replaced, CTS replaced, throttle body has been cleaned, fresh fluids everywhere (not that that should cause a huge issue)
DerekP, with the 4.0L TB, & bored manifold, 33" TSL's, + extra weight [winch, rock sliders, aftermarket bumpers, and heavier rear axle]; it wouldn't surprise me if everything is working fine and that's just what you're getting.
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Old 02-04-2014, 08:35 PM   #6
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Well, 1st question...with all the upgrades that you have done, is your speedometer recalibrated?

Running a 33" tire on a machine that is supposed to have a 27" tire would throw the miles traveled off by almost 1/4th. In other words if you travel 100 miles on your odometer, you actually went almost 125. And with it being 1/4th off, you fuel mileage just jumped up to 12mpg.

A 4cyl, dragging around 33" tires and getting 12mpg is pretty good, considering that the factory rating on that Jeep was 14-16 avg.
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Old 02-04-2014, 09:17 PM   #7
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How modified is the Jeep? Be specific (tires, gears, lift ,etc.).
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Old 02-04-2014, 10:28 PM   #8
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Xpress, if you click on his garage button, he is one of the few that actually filled out the info for his YJ.
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Old 02-05-2014, 12:08 PM   #9
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Is this MPG figure based on the trip gauge? Did you change the stock speedo gear out to match your new tires?
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Old 02-05-2014, 01:31 PM   #10
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the speedo gear has not been replaced, however I am running Autometers GPS speedo, which is actually surprisingly enough within 1 MPH, with me pacing another car who's speedo is assumed to be correct,

as for modifications, I have filled out the Garage section, but if there is anymore you'd like to know specifically let me know.
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Old 02-05-2014, 01:34 PM   #11
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wow I'm getting around 30 mpg out of mine but that's without mods
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Old 02-05-2014, 01:37 PM   #12
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the only thing I haven't replaced that could affect millage at this point is the cat, but reading it with a temp gun it seemed okay (don't remember the exact inlet and outlet temps sorry) but the other day out wheeling (light trail) the cat did get super hot on me thought my floor matt was ready to start melting ! so maybe there is an issue there I was going to just pull it out and put a test pipe in to see if any changes happen and then replace the cat with a new one if need be or if no change put the old one back in, but I can get a Magnaflow universal for around $50.00, so just going to toss It in there
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Old 02-05-2014, 02:06 PM   #13
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wow I'm getting around 30 mpg out of mine but that's without mods
What??????? This is insane... I have a stock yj in terrific shape and i average 16mpg combined. R u sure about this number?
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Old 02-05-2014, 02:16 PM   #14
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What??????? This is insane... I have a stock yj in terrific shape and i average 16mpg combined. R u sure about this number?
I agree. This is the first I've heard of a YJ getting mpgs like that. Most stock 4-bangers get less than 18mpg even when they are in great shape.
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Old 02-05-2014, 02:35 PM   #15
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What??????? This is insane... I have a stock yj in terrific shape and i average 16mpg combined. R u sure about this number?
yeah I figured it up more than once cause I thought I did it wrong the first time, my buddy has a 95 and he gets about the same as I do
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Old 02-05-2014, 03:59 PM   #16
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well that kind of makes me want to cry ! lol
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Old 02-05-2014, 04:32 PM   #17
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every motor is different I guess but I didn't know that they normally got around 16-18 mpg but me and my buddy checked both of ours and it showed us about 29-30 I'll recheck this week and make sure I'm doing it right but I know that 5 gallons will take me 147 miles before I run out which will last me an entire week between work and home
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Old 02-05-2014, 06:45 PM   #18
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I'm guessing you'd be running with no spare, rear seat, doors, bumpers, or top to get anywhere over 20 mpg. Oh, and you're always driving down hill with a strong tail wind. Lol.
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Old 02-05-2014, 07:35 PM   #19
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I'm guessing you'd be running with no spare, rear seat, doors, bumpers, or top to get anywhere over 20 mpg. Oh, and you're always driving down hill with a strong tail wind. Lol.
nope everything is on it lol but those tail winds do help haha but when I get head winds it certainly drops a bit I live down in the hills of Indiana so I'm constantly going up or down one, but most of it is highway
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Old 02-06-2014, 01:15 AM   #20
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wow I'm getting around 30 mpg out of mine but that's without mods
I'm calling bull s*** on this one. No way in hell you are getting those figures with a 3000lb brick and a 120hp engine.
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Old 02-06-2014, 02:09 AM   #21
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ditto. I used to rent a yj everytime I pulled into Hawaii (Navy, go see the world) and would get 20 or so mpg. But that is at sea level and never going over 40mph. My 2.5 with header, hot ignition, K&N, free flow muffler and cat would do maybe 16mpg in the Portland OR area, but when I moved to the mountains of Utah, straight to 12-13 and avoid the freeway at all costs. Elevation will play hell with these things, could be his issue.
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Old 02-06-2014, 04:08 AM   #22
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call what you want but its what I'm getting I'm not going to try and make you all believe me didn't really expect you to since I didn't when I first figured the numbers and as I said I'm not the only one getting that mileage my buddy is too out of his 95
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Old 02-06-2014, 06:18 AM   #23
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call what you want but its what I'm getting I'm not going to try and make you all believe me didn't really expect you to since I didn't when I first figured the numbers and as I said I'm not the only one getting that mileage my buddy is too out of his 95
Post up your miles and gallons next fill up. I would bet there is some mistake. Maybe not even something that is obvious. Such as the previous owner installing a new speedo gear for bigger tires and then switching them back to stock to sell. So your speedo reads fast and your odometer counts more miles then you are actually going.

Otherwise...math error? Or you have both have the 2 20 year old jeeps that can get 30mpg...
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Old 02-06-2014, 07:44 AM   #24
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i can get 14 to 16 around town but on the freeway maybe 12. i have 33s with 5 speed and 4.88 gears. it is a jeep they were not made for fuel mileage..lol
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Old 02-06-2014, 08:02 AM   #25
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Post up your miles and gallons next fill up. I would bet there is some mistake. Maybe not even something that is obvious. Such as the previous owner installing a new speedo gear for bigger tires and then switching them back to stock to sell. So your speedo reads fast and your odometer counts more miles then you are actually going.

Otherwise...math error? Or you have both have the 2 20 year old jeeps that can get 30mpg...
alright I can do that
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Old 02-06-2014, 09:35 AM   #26
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the key word there was "fill". sure you already know, but for all the kids out there, it only works if you fill the tank to the exact same point every time. So ignore the warnings and top up when tracking milage, every tank. And keep a log book of all maintenance and what not, it really helps you figure out when something changes, whether the snake oil actually works, and when to change your oil, rotate tires etc.
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Old 02-06-2014, 09:44 AM   #27
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alright I can do that
I'm guessing here, but I would guess that you're speedometer is off. Either you (or previous owner) put different tires on, or different gears, Etc and never bothered to change the speedometer gear. This could cause a scenario where your odometer could show that you have gone further than you actually have and thus that you are getting better MPGs than you actually are.

Check your speedometer with an accurate GPS at the very least. I'd be willing to bet its off.

All that said, I had a 95 Mazda Protege that routinely got 38mpg+. Everyone said it was impossible esp when the odometer crest 260k, but it was in fact accurate. *shrugs*
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Old 02-06-2014, 10:05 AM   #28
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I'm guessing here, but I would guess that you're speedometer is off. Either you (or previous owner) put different tires on, or different gears, Etc and never bothered to change the speedometer gear. This could cause a scenario where your odometer could show that you have gone further than you actually have and thus that you are getting better MPGs than you actually are.

Check your speedometer with an accurate GPS at the very least. I'd be willing to bet its off.

All that said, I had a 95 Mazda Protege that routinely got 38mpg+. Everyone said it was impossible esp when the odometer crest 260k, but it was in fact accurate. *shrugs*
previous owner put new tires on but they are just slightly bigger I don't have a lift
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Old 02-06-2014, 11:16 AM   #29
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if the pic is actually the jeep in question, those tires are much bigger than stock. Even an inch in diameter is a significant change %wise in circumference. stock tires are tiny.
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Old 02-06-2014, 11:24 AM   #30
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if the pic is actually the jeep in question, those tires are much bigger than stock. Even an inch in diameter is a significant change %wise in circumference. stock tires are tiny.
yup that be it

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