I don't know what kind of mileage you're getting, but I average between 20-24 mpg in my 4-banger. I run a K&N intake and a high flow exhaust system. Also have a throttle body spacer and am waiting to buy a throttle body from a 4.0 to swap in. All that will help the mighty 4-banger run smoother, run stronger, and improve mileage. On top of that, I don't get crazy on the skinny pedal. Shift a little earlier, drive it smooth, and you'll squeeze a few more mpg out of it, guaranteed.

FWIW, I run 31" tires and stock 4.10 gears.

 

Hmm I need to find a jeep with 4.10 gears and steel the axles..lol

 

Find one in a junkyard, sucka. Leave mines alone!

 

Now where do you live Trueblue...

 

High in the mountains, with lots of guns. Feel free to stop by sometime!

 

Google: Hypermiling

I got into a hypermiling kick in my old Nissan 200sx, I had a 45-minute work commute that was about 50/50-town/highway. I went from averaging 33 to 40 mpg after I started reading up on and practicing that stuff.

Higher speeds --> higher drag. Slowing down on the highways makes a huge difference, especially on aerodynamically handicapped bricks like Jeeps...

Stop lights will KILL your mileage faster than just about anything. Your motor's running and you're getting 0 mpg... that'll drag you down. When you see a light changing that you know you won't make, start slowing down early, if you're far enough back and the road's clear enough, it could change back to green for you and you don't even have to stop. That's the best part of practicing this technique... drop into 2nd or 3rd and blow past that rice-burner that was running up your butt earlier and couldn't make the light, screeching to a halt at the light. That always felt good.

Depending on traffic/timing, turn your truck off at the stoplight. The belief that it takes more gas to start the truck than if you were just letting it idle is false... back in the days of carbs and leaded fuel, that was the case, but with modern ignition systems, that's not the case anymore. If the light just turned red, and you know you'll be stuck there a while, just turn it off. Crank her back up when the light changes back. In a 4-cylinder, you'll get an mpg boost.

No lead-foot, but driving like a granny won't really help you either. Your engine is designed to work most efficiently in a specific rpm range. That's not the same as working powerfully. In my old Nissan, the "power-range" was 3k-4.5k, but my efficiency range was pretty narrow and low - 1.25k-2.5k. Accelerate steady, not slow or fast, just steady. and stay in the lowest gear that still gives you enough power to keep moving. The first 4 days I was driving with the Jeep (in the shop already!) I rarely pushed the rpms past 2k. the 1k-2k range had all the power I needed to get to work and back. Though pushing it past the felt good, that's when the gas starts evaporating too fast...

All the maintenance-type tips have already been shared... follow them too, and that will make a big difference.