Hey guys I have a 1997 jeep Cherokee with the 4.0l auto trans and towing package and 31 inch tires with a 2.5 inch lift. I'm currently getting around 209 kilometres a tank and wondering what I can do to increase my mpg and what could be wrongs with my engine since it's getting bad mpg

 

Do you have a check engine light?


When was the last time you did a tune up?


How old are your 02 sensors?

 

Also, when you put the 31s on, did the speedo gear get changed?

 

As far as I know it could use a tune up, and no I didn't change the speedo gear
It has new wires and distribution cap. Should I change the spark plugs?

 

If you change the cap, rotor and plug wires its always a good idea to change the plugs along with it.

Champion coppers gapped to .035

 

What about fuel injectors as well? I've heard that my jeep has a one hole injector and if I change it to a 4 hole one would that work?

 

If you didnt change the gear, the speed is displaying slower then you are going. That equals less kilometers on the odometer compared to what you actually drove. If you are doing km/liters used, the calculation is not correct. You might be off a few KPL which would eplain why the fuel consumption is bad.

 

stockers to 31's will net about an extra 15-20(miles) to a tank. easiest way until you swap out your speedo gear is to take the ratio difference of your 2 tire sizes and multiply your odometer mileage by that ratio. Should be like 1.1 or 1.09 for a 28" to 31" tire. so 209*1.1=229.9. then divide your gallons/litres used. Yes you can change the injectors to a 4hole, but mileage increase will be minimal at best. most report better "driveability"

 

I'm surprised no one has come along yet and said: you're driving a lifted Jeep, if you care about gas mileage, get a Yaris.

 

 

lol

 

I have a Chevy Metro 3 cyl 5 speed. 40+ mpg on the highway.

Basically, XJ efficiency boils down to meticulous maintenance. Be mindful of more than just motor oil and filters: gear oils, ignition health, tires, alignment, O2 sensors, fuel pressure, compression...

Without the right speedo gear (very easy to swap), you need to use math to compensate for your 31's, but without regearing, 31's on stock gears is a problem for your efficiency regardless. Any lift also kills aerodynamics as do bigger tires. Bigger tires also cause much more drag especially if they're aggressive.


P.S. Distance per tank is a terrible unit to use. Calculate a proper mile per gallon or liter per kilometer.

 

That's pretty terrible. Definitely lower than a "lifted brick" should get. Are your brakes dragging? Any U joints trying to seize? Tires flat?

 

My 99 XJ 4 1/2" lift and with about 100# of weight in the cargo area at all times still gets 15-16 mpg highway 33x12:50x15 MT tires, 4.56 gears.

 

There's your biggest problem right there.

Kilometers per tank is garbage. You have no idea what your fuel economy is.

Worse, you probably think you know.


Take the gallons reading off the pump and divide that by miles driven (corrected for your tire diameter!).

Any other method is WRONG.


When you have an actual MPG number that means something, then you can look at improving it.