Tires and Gas Mileage? Good or Bad?
 

Will bigger than the stock tires give me better or worse gas mileage on my 97 f150. Came with like 235/ and I wanna put 265/ on her. What do you think and use?

Probably worse. They'll effectively lower your gearing which might increase fuel mileage, but they'll be heavier and take more power to turn. What kind of mileage do you get now with what engine/gear ratio/2wd/4wd?

It depends on your powertrain. Too tall of a tire can hurt milage, but so can a tire that is too short. You have to find the "sweet spot" which is usually one of the OEM combinations.