I agree with the above comments about the excessive speed. I`ve read studies about wind resistance that say that when you drive above 60mph you wind resistance increases dramatically, greatly reducing your MPG. also I gained 1 mpg with a drop in K&N filter, I confirmed it many times both before and after it was installed on an 03 Dakota 4x4 ex. cab w/ 3.9 5 speed 355 gears(got about 18.5mpg) my 08 Dakota ex. cab 3.7 auto w/392 gears gets about 19.5mpg and lots more HP than the 3.9