I have an '02 Regular Cab with the 3.9l V6 and I am only getting 12-14 MPG whether I drive it hard or easy. Highway or city. Any suggestions for better mileage?

 

Last time it had a tune up? How old are the O2 sensors? Tire pressures? Tire size vs. gearing? WAY too many possibilities here.

 

My '97 (3.9 liter) never did better than 15mpg. I just got a 2004 with the 3.7 V6, and it managed slightly better than 20 mpg on a 200 mile highway trip. (No extra passengers, and no cargo.)

 

3.9L out, Gen 3 Hemi plus 8 speed in. Should get you at least 25MPG, but it'll take a few weeks for the fuel savings to cover the cost of conversion. If power's not important, 3.6L plus 8 speed. You'd probably see the fuel savings break even a few days earlier.

The stuff that'll work on your current engine has already been covered.