98 ZJ with 4.0L with 177,000 miles. I am averaging in town 12.5 mpg. What can I do to increase mileage? I plan on getting an alignment and my tires have 50lbs, but what else could I do to help.

 

tune up and front o2 sensor

 

50 psi in your tires!?!??!?!?!

never! most tires are not designed to be run with that high of a pressure, and it may cause a blowout!

lower your pressure to the correct range of 30-32 (for stock size tires) and then you can work on the mileage problem. my recommendation: free-flowing intake and exhaust upgrades can increase mileage, as well as making sure all drivetrain fluids are clean and are changed regularly.

 

12.5 seem low to me. I'm averaging 15.3 in city only in a 93 ZJ with 169,000 on the clock. I would look into maintanance items first, air filter, plugs, wires, cap and rotor. Also the front o2 sensor might be a little lazy you can check that if you have access to a scope. There is not a lot you can do to increase fuel economy above the factory specs. little things like a intake and exhaust helps a little. Changing all your fluids to synthetic can also help but on older cars it can cause leaks to show up or get worse.

 

Start with a tune up. What size tires? 4wd or 2wd?

 

I plan to do the plugs, wires and cap. I have 245-75-15 general at grabber tires.

If it was an O2 sensor wouldn't it throw a code?

 

Not necessarily. Make sure your air filter is in good shape as well. People always say to do intake/exhaust to increase mileage, and it might bump it a couple mpgs, but I wouldn't hold my breath on that. Regardless, yours seems low (assuming your driving style and location aren't major factors), so I'd start with a good tune up first.

 

Just bought a 1994 ZJ am going through these post. Your tire pressure is marked on the side wall. A quick check over at Tire rack for those tires shows between 44-50 psi, so don't worry too much about a blow out.

How long have you had yours? Has the mileage been going down or has it always been about that?

EPA shows 14 mpg for around town. I have seen these Numbers both high and low compared to reality.
http://www.fueleconomy.gov/feg/bymod...Cherokee.shtml
1.5mpg off may just be how you drive. I get a consistent 22 mpg on my daily driver and my wife will drive it for a week and get no more then 18 mpg.

I will echo what others have said about maintenance items, Filter, plugs, wires, cap, rotor, all good places to start. It also wouldn't hurt to try a few bottles of Fuel injector cleaner.

 

#1 factor is driver bahaviour and proper tire inflation, the money you spend on all that other stuff(unless it has to be replaced) will offset any savings in mileage. Use the cruise control whenever you can and stay off the throttle.

 

 

I have to echo what RaiderMike said. It's mostly driver behavior that affects the MPG the most. I own a Bone Stock 01 GC Laredo 4WD with the 4.0L and I get about 17 around town and 23 highway. Aside from making sure the vehicle is in a high state of tune, feathering the throttle will yield you your biggest increase over any other add on that you can buy. I get up to speed then back off the throttle and give it just enough juice to maintain my speed. My overhead console fluctuates between 16.5 and 17.7.

The only time I notice that I am getting that low of a MPG reading is when we had 16" of snow dumped on us here in the VA Beach area and I was driving around in 4WD. So the next question is, not to insult your IQ, but are you sure you are in 2WD?

 

gentlemen: the pressure marked on the sidewall is the MAXIMUM pressure for that particular model of tire, NOT the correct pressure for your vehicle/tire combo.

while the maximum may be 40 or 50 psi, the correct pressure for your vehicle is about 30-32 psi.

 

^
+100,000

Most beneficial thing you can do - change your driving habits.

 

agreed on the driving habits. i cant complain my mileage is low because i have a very heavy foot.

and thanks for the support, Bustedknuckle!

 

Running too low of pressure/under inflation can lead to them over heating, tread separation and tire failure long before too much pressure will cause a blow out. Is all I meant. Too much PSI can/may cause stability and handling issues. If your tires max cold psi is too far from the Recommended PSI on the door chance are you have the wrong tires.