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11 miles per gallon

blue95xj

<---- Brrrrrrrr!
Location
arnold, mo
yes i know another gas mileage question, but this is ridiculous.

I've got a 95, 4.0, aw4, 3" lift, stock 3.55s, 31x10.5 bfgs, and a homebrew intake. I used to get 10 with a drop in k&n before the intake. i will admit i am a little heavy on pedal but even when i'm not i still only get 225 to a tank.
I have recently replaced the o2 sensor no results good ol' cleaners don't help, new fuel filter and still nothing. i'm sure smaller tires would help but that just looks retarded, i'm also gonna drop the front shaft for the summer (just got done reading post, interesting). also thinking it could be a clogged cat or vac leak. any other suggestions would be greatly appreciated.
 
I have a 92, 4.0, aw4, 3" lift, 3.55, 30X10.5 and I also get about 225 miles out of a tank of gas and I am not a fast driver. So I would be interested in any information on improving gas mileage. Also I just replaced my cat, my O2 sensor is relatively new, and I passed emissions testing with flying colors.
 
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Did you correct your speedometer? A 31 is about 110% the height of a stock one. If you haven't corrected your speedometer yet, multiply the distance on your trip odometer by 1.1 and then calculate your mpg.
 
I keep my rig tuned with good quality parts, but my mileage was starting to fall off. I started replacing some of the stock sensors, it's an '88 so I felt it was due regardless. Nothing seemed to really make any difference and the mileage was down to 11-13 MPG, untill I replaced the injectors. My mileage jumped back up to 16-18 and 18-20 when all H-Way.

I also think the stock gearing is part of the problem. When you went to 31.0" tires you need to adjust the gearing to maintain the RPM's. The 4.0 motor doesn't like to be lugged down. Good Luck

Woody
 
Bone stock 92 4.0, AW4 3.55 with 200K on it, for the last 5000 miles the overall mpg is 19.4. I write down everytime I put gas in it and the miles. 5338 miles and 275 gallons. 235X15 tires.
I like to check it after long distances, average in city and country driving.
 
tsgolo said:
How many gallons does it take to fill up when you've driven 225 miles? I take it the 225 is based on the odometer? dn

i have never driven 225 on a single tank this is based on how much it takes to fill up x the mileage on the trip = 11 and some change rounded down to 11 and then x 20.5 gallons = 225.5

Mambeu said:
Did you correct your speedometer? A 31 is about 110% the height of a stock one. If you haven't corrected your speedometer yet, multiply the distance on your trip odometer by 1.1 and then calculate your mpg.

spedometer is correct, i drive by the giant radar deals that the numbers flash at you and tell you if you are speeding (as if you didn't already know) and is always right on.

and i did forget to mention the accel cap and rotor and taylor 8 mm wires (no coil yet). but did not see any thing from those either (wasn't expecting much if any)
 
blue95xj said:
i have never driven 225 on a single tank this is based on how much it takes to fill up x the mileage on the trip = 11 and some change rounded down to 11 and then x 20.5 gallons = 225.5

Not sure I follow this. For figuring out mileage, take the miles driven, divide by gallons to fill up. 275/18=15.27 or about 15 mpg.
 
blue95xj said:
i have never driven 225 on a single tank this is based on how much it takes to fill up x the mileage on the trip = 11 and some change rounded down to 11 and then x 20.5 gallons = 225.5
This makes it sound like you're driving eleven miles, filling up with one gallon and then multiplying by the tank's capacity. That's really weird, if you're actually doing that. The right way to calculate mpg is to start with a full tank, drive for a while, and then fill up again. The miles driven divided by the number of gallons you put in is your mpg for that tank.
 
regearing is the answer i went from 10 mpg to 17-18 mpg with 4.10s and on 31's. and not being that easy on the pedal after breaking them in.
 
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blue95xj said:
spedometer is correct, i drive by the giant radar deals that the numbers flash at you and tell you if you are speeding (as if you didn't already know) and is always right on.

i think what he was getting at with the spedometer being correct is not how fast you're driving but rather how many miles you're driving, as the odometer effects both.
 
I run 33" tires with 3.73 gears ('87 Comanche 4.0L, 2wd 5 speed and lifted 5" with the 4x4 front axle in and waiting for the tcase/trans to be installed) and I get 20 mpg (300 miles gets 15 gallons on average since I drive over 1/2 my mileage on the freeway) I find the cam of the HO 4.0L requires lower gearing to get power where it should be, (power peaks at higher RPM than Renix rigs) so I would run probably 4.10 with 33" or 3.73 with 31".
 
xj_mike said:
Not sure I follow this. For figuring out mileage, take the miles driven, divide by gallons to fill up. 275/18=15.27 or about 15 mpg.

yes i meant divide i was in a hurry and was not thinking, i divide the mileage by the gallons which = 11 then 11 times 20.5 or 20 = 225.5

sounds like regearing is the key that unlocks better gas mileage

thanks guys
 
blue95xj said:
yes i meant divide i was in a hurry and was not thinking, i divide the mileage by the gallons which = 11 then 11 times 20.5 or 20 = 225.5

sounds like regearing is the key that unlocks better gas mileage

thanks guys

It will take a lot of miles at higher MPG to offset the cost of re-gearing. I suggest you determine how much money you will save in fuel by regearing. The lower MPG and subsequent higher total fuel cost of your current setup may be less expensive than regearing.
 
91 Jeep Project said:
That isn't the only reason to regear.

No duh.

For this discussion, though, increased MPG was presented as the only reason to regear. I am sure the "know it alls" on this board will soon point out the myriad of reasons to regear.

It makes no ecomonic sense to regear for the sole purpose to increase MPG and to "save money" because of high gas prices.
 
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