I've got a 2002 Expedition and the best I've ever seen is 18MPG - I have no idea how someone pulls 29MPG from an 88 F150 - maybe there's a secret formula in the fuel in your neck-of-the-woods!

I would think to get a 50% increase over advertised highway MPG one would certainly need aluminum heads, and an aluminum engine, all aluminum frame, titanium drive train, all carbon fiber body and 22" true magnesium wheels with 45" tires with good JATO setup..

If anyone helps you get 28MPG out of your rig, let's talk about some patents and big buck opportunity!!

Good Luck!
Glenn