A K and N filter would be nice, but how long would it take to pay for itself?

 

Adjust the nut behind the wheel first. You aren't in a race, you don't have to be first. Leave a bit more room between you and the car in front, watch a couple cars ahead, when they brake, take your foot off the gas. Drive without using the brakes as much as possible. Drive with the throttle like there is an egg under your foot. Remove your roofrack if you have a big one on top. Run a little more air in your tires than normal. You HAVE to adjust your habits, hence, adjust the nut behind the wheel.

My ZJ, 95 4.0 automatic, NP242, 3.73s. I have a 2" BB lift over Upcountry springs, and am on 31s. I am AVERAGING 20MPG. I do not measure any tank that I have been trailriding. On the street and highway, I run 35psi in the fronts, ad 38psi in the rear. Harsh ride? Yes. And my average? Includes driving my carpool (4 of us in the pool), 50 miles each way, including a mountain pass. And, we are above 4000' above sea level. I've seen as high as ALMOST 24MPG in a tank. I don't believe the overhead console MPG info. Though, it is fun to watch the current mileage while driving and seeing what type of driving does what. My mileage WAS a hair better on 30s though...

Also, I get 36 to 38 MPG with my 2003 Neon. EPA rated about 30 or so... My son has seen almost 40 (39.8) with my Neon.