Horrible MPG unsure why

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Oct 2, 2014 | 01:05 PM

#16

cherokee001

Member

Joined: Jan 2011

Posts: 180

Likes: 0

From: Central NJ

Year: 2000

Model: Cherokee

i have 3" lift, 31" tires and get about 12-14mpg, OEM gears. Not sure if i should regear.

Oct 2, 2014 | 10:39 PM

#17

dvldog

Newbie

Joined: Oct 2014

Posts: 6

Likes: 0

From: middle TN

Year: 1996

Model: Cherokee

Engine: 4.0

Quote:

Originally Posted by cherokee001

i have 3" lift, 31" tires and get about 12-14mpg, OEM gears. Not sure if i should regear.

Me personally, anytime I lift something and put bigger tires on it I regear. That being said I have yet to regear my new project.

I have a 96 xj 4.0 with a 6.5" lift on 33's, using a GPS to track miles and I'm getting around 14-15 in the city.

Oct 3, 2014 | 01:19 AM

#18

RabidWolf1966

Newbie

Joined: Oct 2014

Posts: 3

Likes: 0

Model: Cherokee

Wow, and I thought my 14mpg was bad

Oct 3, 2014 | 02:32 AM

#19

Muddz

Seasoned Member

Joined: Nov 2013

Posts: 290

Likes: 1

From: USA

Year: 1995

Model: Grand Cherokee (ZJ)

Engine: 4.0L

Quote:

Originally Posted by TrystanK

i have a 1998 cherokee with the 4.0, and i just did a 154 miles on a 19gallon tank which comes out to 8.1mpg. its lifted 6.5 inches and on 35's and not regeared, in no way am i expecting high teens but the high single digit doesnt seem quite right. curious to see if anyone else has had this same problem and if so how you went about fixing it, or any ideas on how my mpg is so low?

Have you changed the speedometer gears?
If not your odometer is reporting lower miles than traveled.

35 = current tire size
28.29 = stock tire size 225s, or 215's = 27.7

35/28.29 = 1.2372

154 odometer miles

Actual miles travelled 154x1.2372 = 190.5288

Fill up = 19 gallons

190.5288 / 19 = 10.0278 mpg.

Other factors:

Tread design, air flow, lift, intake, payload, exhaust, sensors, etc. ...

When using 35s your differential gears should be 411 or higher.

http://www.4lo.com/calc/geartable.php

http://www.4lo.com/calc/gearratio.php

http://www.dakota-truck.net/TIRECALC/tirecalc.html

Last edited by Muddz; Oct 3, 2014 at 02:58 AM.

Oct 3, 2014 | 04:45 AM

#20

HudsonN

Seasoned Member

Joined: Jul 2012

Posts: 484

Likes: 3

From: New Milford, CT

Year: 1999

Model: Cherokee

Engine: 4.0

All I can say is I'm happy I dd a stock XJ and only use the built one as a weekend warrior.

I average 330 miles per tank. Normally takes 17-18 gallons.

Nov 12, 2014 | 06:44 PM

#21

xjallseasons

Senior Member

Joined: Feb 2011

Posts: 664

Likes: 29

From: Arizona

Year: 1996

Model: Cherokee

Engine: 4.0

I was getting 17 or so with 33's, 4" lift and OEM gears. Then I got into an accident, replaced all the damage and know I need a front end alignment. It sat for around 4 months and once I got to driving it I was around 8 to 10 mpg.
A friend said I should use Seafoam on my next full tank of gas. Hopefully after the front end alignment and seafoam, I should see better mpg's. I know that changing gears is next on the horizon, but these immediate fixes are cheaper and better on my budget. I only drive 10 miles a day for work so its not a big deal. I JUST WANT MORE!

Nov 12, 2014 | 09:37 PM

#22

s346k

CF Veteran

Joined: Feb 2012

Posts: 2,282

Likes: 18

From: central IN

Year: 1997

Engine: 4.0

I recently lifted my jeep ~2.5" and lost almost 2 mpg exactly. it's down to avg 19.8 now. I'm expecting that to drop further if I put larger tires on it. so much for my unicorn 22 mpg jeep. I almost want the saggy leaf syndrome back haha.