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?

 

Your lift and tire size don't help much. Also the weight you carry and how heavy your right foot is makes a huge difference. I'm at 4.5/32s and I avg 13.8 mpg. I drive it pretty easy too

 

Heavy right foot?

 

You have any cels? Does your exhaust smell rich?

 

Are you calculating the fact that less miles show on odometer to how many you actually went with 35s over stock size? On my 33s if I went 200 miles, it actually came out to 220 miles. To a full tank I get around 180-190 on the odometer which is around 190-205 actual miles.

You can't expect much running stock gears, on a high lift, with that size of tires. Honestly I would consider getting 10mpg great mileage on 35s and stock gears.

 

I average about 15 mpg on 35s, 3.73 gears and a 5 speed. One HUGE thing you need to do is get your Speedo gear replaced, so you aren't speeding and your mileage on the odo rings truer

 

On the one tank of gas ot was mainly in town with one off roading trip so I could see how that woukd drop my mpg. My Speedo is off by about 12mph, I didn't even think about the fact that I'm going farther then it says. Thanks for all the help, I'm new to the cherokee world but I absolutley love it.

 

Speedos aren't off by a certain speed they're off by percentages. So it's not 12 mph off all the time. I think since you're running 35s it would be about 20% off if I calculated that right.

 

You need to re-gear badly 3.55's with 35" tires and 6 1/2" lift to boot equals very poor mileage period, even with the speedometer being off.

 

You're lucky to even get that.

I'm running 33's with 4.56's and I still only get around 10 MPG in city. That's with 784 injectors and complete tune up.

 

I have the same setup and get 16 MPG highway and 12-13 MPG city and am just thankful for that.

Differently regear anyways besides the bad gas mileage, so much more fun to drive correctly geared.

I would look at TPS, MAP, O2 sensors, spark plugs and cleaning your fuel injecters for starters. Maybe check out your fuel filter and pump too.

Definitely check your exhaust and see if it is rich like what Mr White suggested to see if it is super rich or not.

Also make sure your air filter is clean, that makes a bigger difference than you think and often gets forgotten about.

 

Excellent point. I use the county mile markers and long sections. I'll write down what my odometer read and what the signs said for maybe three 15 mile stretches, then average the result to see what % I'm under reading.

If it were 4%, 100 miles on the odometer would really be 104 miles. If the speedo said 50, you'd really going 52. 25 would really be 26, 75 is 78, ect...
(on a calculator, you might just punch +....4....%)(to add the 4% to your miles, before you divide by Gals.)

THEN one tank isn't really much of a test. Any little angle filling up, different pumps....Gotta go at least a couple of tanks and keep accurate numbers to get a meaningful MPG figure.

4% was just a random example.

 

I've got brand new NGK's, 784 injectors, brand new air filter, new bosch O2 sensors.

Never replaced the TPS/fuel pump but I've never had a CEL for anything like that or any problems related to them.

 

This is what I'm seeing as well, tracked over 8 months. Used a fuel log app.
4.56 gears, 35's, automatic. Calibrated the speedo to within 3% (which was better than stock at 10% low). Confirmed by GPS and roadside radar markers.

I only see 8mpg on the trail in 4lo.

The stock gearing is way too low for 35s, you have to dig your foot deep to go anywhere, meaning ... Bye bye gas mileage (not that a Jeep ever had decent economy to start).
My solution, get the damn MJ back on the road so I can stop daily driving my trail rig. It was never built to roll the highway.

 

Did this bad mileage start after the lift/tires or other mod?