Matts Jeep

Just put a 3 in lift on my 98 xj and finally got some 31's to run on it. But my gas milage has gone down the drain. i put some Savero komodo M/T's on it. could it be just those tires or would that happen with any tires?

askingxforxit

Bigger tires = less gas mileage especially with mud tires

Atmos

Any over sized tires will rape fuel economy
You need more torque to match your big tires

Gorillaxj

X2! all you can really do is make sure all you general maintenance is good, plugs, cap, rotor, wires, air filter, fluids ect... might gain a little back if anything has been over looked. but For the most part what it is, is what you get!

Power73

Maybe swap gears?

Matts Jeep

Any idea what gear ratio i should have with the new tires, or what would work better?

bzauche

Depends on what you use it most for. Mine is at 3.5" and 31's, and I'm still at stock 3.55 gears. Mine stays on the road 95% of the time, so 3.55's are OK, but I'd love to have 4.10's. If you plan on staying at 31's, and you want to regear, most people would go to 4.10's. If you plan on going bigger, say...33's, you might want to regear in anticipation of those, so you'd go for 4.56's. Hope that helps!

Rock Toy

Well, there isn't much in the way of information about your Cherokee, like is it an auto or a manual? The auto will probably have 3.55 to 1 ratio where the manual has a 3.07 to 1 ratio that is numerically to low to begin with. Have you corrected the speedometer? If you started with the 215x75 r15 which are about 27.6 inches tall and go to a 31" that is 30.8 your speedometer will be way off. Were your old tires a highway tread? I'm not real sure, but I think the tires you named are a very aggressive max traction type tire and that could effect fuel mileage.

BrofessorXJ

You only want to regear once so make sure it's to go with the tires you will want to eventually run. For now why don't you try some bolt on's to improve fuel economy a bit. Examples are a cowl intake, bored tb, 703 or 784 injectors, 99+ intake manifold, headers, open up the exhaust to 2.5" with a high flow cat and muffler. That should help a bit and restore some lost power as well.

Kuro89

also your speedometer and odometer are wrong, so if you are going to re gear you will want to get the proper speedo gear for your combination of tires and gears

AVjeeper

This thread may be helpful reading.
https://www.cherokeeforum.com/f2/horrible-mpgs-128124/

bnkk

I just made a post other day about people thinking there milage is bad. You shouldnt have lost much you may want to try some of the ideas on what causes it if you are sure you lost mileage.

Matts Jeep

thanks for all the info guys. its really helpful. im still learning and im trying to do this right. ya the new tires have a very aggressive tread and i plan to keep 31's on it at the largest. i have to drive 6 miles of dirt road a day just to get to town and back home and i plan to keep the jeep for a while. yes its an automatic, with a straight 6-cyl. once again thanks for the info