Improving fuel mileage...
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,579
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Low-tech, but still the best "gauge" of engine load.
A MAP sensor is just an electronic version of it.
CF Veteran
Joined: Mar 2012
Posts: 1,414
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From: whiting
Year: 2001
Model: Cherokee
Engine: 4.0
Seasoned Member
Joined: Oct 2011
Posts: 275
Likes: 0
From: San Diego California
Year: 1988
Model: Cherokee
Engine: 4.0 Liter Inline Six
The way I see it is, I didn't buy my XJ for fuel efficiency. If I wanted a fuel sipper I would have gotten something small with a 4 banger and a 5 speed.
I figured it out by doing the math from how far I drove to what I had in my tank. It was right around 16.8 I went from Fort Leonard wood Missouri to Effingham Illinois before I my gas light came on and I filled up. So I'm pretty sure the numbers are accurate.
CF Veteran

Joined: Jul 2012
Posts: 4,104
Likes: 2
From: San Antonio, TX
Year: 1996
Model: Cherokee
Engine: 4.0L
-Run the lightest wheel/tire combo you can
-make sure your engine is properly tuned up (spark plugs,02 sensors, filters, fluids)
- a cowl snorkle k&n filter will help along with IAT relocation
-703 neon injectors
-60mm throttle body
-e-fan conversion
-proper gears for your tire sized (and correct speedo gear)
-hesco water pump
- keep the weight down as best you can
- dont drive faster than 65 ever
Im getting 15.5 mpg right now with: winch and winch bumper/ tire carrier/sliders/ tire carrier/ highlift/skids/33s/4.10s and most the performance mods I mentioned.
I could probably muster mid 16s with out the extra weight and the engine/trans have 230k on them
-make sure your engine is properly tuned up (spark plugs,02 sensors, filters, fluids)
- a cowl snorkle k&n filter will help along with IAT relocation
-703 neon injectors
-60mm throttle body
-e-fan conversion
-proper gears for your tire sized (and correct speedo gear)
-hesco water pump
- keep the weight down as best you can
- dont drive faster than 65 ever
Im getting 15.5 mpg right now with: winch and winch bumper/ tire carrier/sliders/ tire carrier/ highlift/skids/33s/4.10s and most the performance mods I mentioned.
I could probably muster mid 16s with out the extra weight and the engine/trans have 230k on them
CF Veteran

Joined: Jul 2012
Posts: 4,104
Likes: 2
From: San Antonio, TX
Year: 1996
Model: Cherokee
Engine: 4.0L
I more than know that im not driving a prius but if theres room for improvement id like to take advantage of that.
But to each his own
Unless you have spent the money on a full gear change to match the tire size you are running or bought the correct size speedometer gear your "horrible" gas mileage is not as bad as you think. Spend $40 buck on one of these first to match your tire size.
Newbie
Joined: Dec 2013
Posts: 10
Likes: 0
From: between continents
Year: '99 & '00
Model: Cherokee
Engine: 2.5 L Diesel VM Motori & modified 2.5L Diesel VM Motori
Throw on pure street tires with the same diameter.
After 9 month you have saved the expense for the extra tires and your offroad tires last longer too.
The couple of times you go offroading isn't worth to spend the extra fuel continously.
After 9 month you have saved the expense for the extra tires and your offroad tires last longer too.
The couple of times you go offroading isn't worth to spend the extra fuel continously.
Seasoned Member
Joined: Aug 2013
Posts: 405
Likes: 0
From: Connecticut
Year: 1998
Model: Cherokee
Engine: I6 4.0
I would just be afraid that tires would start dry rotting from sitting around.
Member

Joined: Apr 2014
Posts: 217
Likes: 1
From: Sioux City, IA
Year: 1994
Model: Cherokee
Engine: 4.6L Stroker
I don't know about all this MPG I see here, I had a 96 4dr xj with a 4.6 stroker in it and a 5 speed with a 3" lift and Timberline MT 31's on it and 3.73 gears, had the correct speedo gear and my daily highway driving was around 20 mpg and in town was around 16 mpg. My current 94 2dr xj with a 4.6 stroker and a auto with a shift kit and 4.56 gears and 33" Discoverer STT gets about 18-19 mpg on highway and 14-16 in town and I haven't even put in a cold air intake or put my new header and high flow exhaust system on. I don't know maybe I drive like a grandpa compared to you guys and just don't notice it. I always thought i had a bit of a lead foot but seeing what you guys get and what my friends XJ (13mpg) gets I guess I don't know the true meaning of lead foot. Also neither of my XJ's had aftermarket bumpers or wenches on them.
Senior Member
Joined: Jul 2012
Posts: 860
Likes: 0
From: middleburg fl
Year: 1998
Model: Cherokee
Engine: 4.0
the point i was making was if you havent regeared your speedo to be accurate with 33 inch tires and you are using the trucks odometer to figure ouit how far you drove then your numbers are wrong, very wrong 33in tires rotate less per mile than a stock tire so that means for example every mile indicated is maybe 1.1 mile (math gurus chime in here) or more so every 10 miles is 11
ok i just looked it up if you havent redone your speedo you are 16.1% off i found that a stock tire is 27.7 inches tall compared to your 33in tall
so you can add 2.7mpg to your figure which gives you 19.5mpg which aint too shabby
additionally at 60mph indicated on your speedo you are doing 71mph
heres some of the sites i used
http://www.onlineconversion.com/bigger_tires.htm
http://tire-size-conversion.com/tire-height-calculator/
http://www.onlineconversion.com/percentcalc.htm
Last edited by kennzz05; May 14, 2014 at 11:51 AM.
I see what you mean, and it hasn’t been regeared.I just figured out how far I drove and how much gas I used and did it that way. But yea at 60 I’m doing 61-62 and at 70 I’m doing 83
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