Low shift points will help with the 4.0L straight-six, but I doubt it
will help with the 4-banger. They like to rev, and make more torque
and HP between 2500 and 3000 rpm.

I recently clocked nearly 28 mpg. in my TJL. My secrets:

1. Gentle acceleration, low shift points. Good for 4.0's, not so good
for 2.5's. I often shift at 1200 rpm. around town. I don't give a
damn about butt-sniffing, stoplight-racing morons. They eventually get
a clue and go around me.

2. Make the lights. Cut back your speed around town 5-7 mph. and you
will more easily be able to cruise through green lights. Let the
Bohemian Honda types race each other! They get great fuel mileage
regardless how badly they drive, so they are of no concern. Jeeps are
heavy. Starting/stopping eats fuel, especially when your ride weighs
nearly two tons.

3. Shift progressively. This is something that Semi drivers do
routinely, and it applies here. I have a 13-sp. transmission in the
Big Truck, but I don't use every available gear if I don't have to.
You can skip a gear or two to save fuel and wear-n-tear if you do it
gently.

4. Lower rolling resistance. I spend most of my time on pavement, so I
avoid running off-road tires. I also watch tire pressure pretty
closely. You can run highway tires between 32 and 34 for better fuel
mileage and longer tire life. Another way to lower resistance is to
limit freeway speed to 60 mph. Tuck in 100 ft. behind a Semi for even
better results, but don't tailgate.

5. Use decent fuel. Cheap fuels are usually cut with alcohol which
lowers fuel mileage. You don't get something for nothing. Stick with
good quality fuels that avoid excessive amounts of alcohol for better
performance and fuel mileage.

6. Avoid warmups. Even in very cold regions, it is not neccessary to
warm an engine longer than it takes to build normal oil pressure before
you drive away. Do limit your engine speed however until it warms up
to at least room tempurature.

7. Use synthetic lubricants. You will see a 10 degree reduction in
internal engine temps and a 2-5% increase in fuel mileage by using good
quality synthetics in the drivetrain.

8. Right-hand turn routes. UPS discovered this one a long time ago.
If you are consolidating errands around town, arrange them in such a
way that you make all right-hand turns. This saves a lot of time and
fuel.

9. Shift to neutral! If you're running an automatic transmission,
shift to neutral when sitting at a long stop light. While drive is
selected, the engine is constantly under load, which uses more fuel and
creates a tremendous amount engine and transmission heat. Shift to
neutral if you anticipate sitting more than 15 seconds for cooler temps
and better fuel mileage.

10. Don't downshift when comming to a stop. Not only does this use
more fuel, it cuts your clutch life in half. Use the brakes - that's
what they were designed for.

11. Keep your engine in excellent tune. Do a tune-up yearly.
Investigate MIL's immediately. Buy a code scanner and learn how to use
it. Don't use el-cheapo filters or spark plugs - they fail quickly.
Avoid gimmick add-on's and fuel additives.

12. Park in the garage at night. This keeps the night chill off the
drivetrain and allows a easier start-up and quicker warm-up when
started in the morning.

13. Lighten it up! If you don't use the back seat, pull and store it.
If you're just plogging around town, you don't need 200-lbs. of rescue
equipment in the back, so leave it in the garage.

14. Circle the city. When I drive from one end of town to the other,
I don't drive straight through: it's full of stop-signs, lights and
traffic. Instead, I always plot a path AROUND the city, in a clockwise
fashion, of course, to take advantage of quicker right-hand turning,
using lesser-traveled rural roads.

15. Hold your lane, avoid braking. Another Trucker staple. The best
drivers stay in their own lane, and only change in anticipation of a
turn. If you have to hit the brakes to make a turn, you're driving too
fast. Every press on the brake pedal is fuel you have wasted. Slow
further back from your turns enough that you can drop a gear and make
the turn without having to hit the binders for maximum efficiency.
Forget about the dorks on your bumper - they don't know what you know.

16. Don't run bald tires. After 50-60% of the tread is gone, rolling
resistance increases dramatically and bad weather traction suffers.
Spend whatever it takes for the best quality and longest-wearing tires
you can get. Name-brand tires with heavier, stiffer sidewalls offer
better fuel mileage and longer wear. Avoid cheap tires like the plague
they are. Avoid fitting anything wider than OEM specs as well: the
wider the tires, the more rolling resistance you have to overcome.

Enough for now. I don't see any reason why you can't get 30+ mpg. in a
4-banger Jeep. A little knowledge will take you a long way.

-JD