what mods are going to yield the highest gains in fuel mileage?

synthetic fluids can get you 1-3 more mpg

cheap or free options:
*bump up the tire pressure to the max recommended
pressure stamped on the tire itself. reduces rolling resistance

*drop your normal driving speed by 5mph when possible. reduces drag

*Remove ALL extra stuff from truck that you do not need. Any weight you can remove can make a small difference. reduces rolling resistance

*Keep it waxed. reduces drag

*An old trick from drag racers years ago is to not "top off" the oil level, and run it at the middle of the "safe" level (half quart low). this will decrease the amount of oil the crank comes in contact with, freeing up some power.

*run with the windows down up to 45mph, then roll up the windows and use the AC for anything higher than that.

*on long road trips, pull your mirrors in against the cab. reduces drag

moderate to expensive:
*Complete CAI system with dry flow filter, and heat shield.

*Some say that headers (long tube style) net some fuel economy, but at 500-1400 bones your not going to break even on cost vs fuel savings very fast (if ever)

*Shorter tires. EX: if you have 20" rims the factory tire is 33" tall. Step down to 31"-32". BUT to see the savings you will need a Superchips tuner to adjust the tire size.

*Lighter weight rims. Ex: factory 20"s with tires weigh in over 70lbs a piece! 1lb of rolling mass equals 8lbs of static weight.

*park it and drive a civic.

I actually bumbed my tire pressure on my stock 33s to 37 psi. Handles way better and im sure I get better mpg. Drive a civic??? Radther ride my bike. Actually quicker too. Beaten my friends mazda up to about 23 mph.

I hear a hydrogen generator can give you a boost of 5-7 MPG. A friend of mine put one on his Ram 2500 and sees a 5 MPG increase. Anyone else hear any sucess stories?

Riding a bike means I might get excercise and lose weight, plus it rains here too much. I would not be caught dead in a Civic.......I drive a Sentra.