98 F150 4.6 stock
 

I would like to know which programmer would be the best for gas mileage. Need to know fast before gas prices empty my pockets.

They aren't designed to improve mileage. Any mileage increase is offset by the cost of the premium fuel to run them in performance more.

Which programmer can compensate for different size tires (255/70 ---> 245/75)? Bought the pickup and the tires they put on are of different size than what it calls for. a little power would be nice also.
Thanks

Yep thats true the price is offset and the superchips does allow you to adjust for tire size.. I first went with a Hypertech which I promptly sent back for a Superchips my mileage did go up but only after I had to run premium. But I look at it this way, I'm paying the same amount per mile and getting more performance so what the hell.

Yea, the superchips tuner allows you to change for tires sizes except for the 97 and 98 model years. They require a gear change and the tuner won't work for that. You don't get any better gas milage at least not enough to offset the cost of premium fuel and tuner.

Save your money if you want to save on fuel costs, the tuner won't work. Keep the truck tuned, tires inflated and off the accelerator. Another way to save on fuel costs is to leave her in the driveway. :-X24

Tuners and chips are meant for power, the mileage is just a bonus that helps you justify getting it with your wife or parents or whoever you might have to answer to.