2004 f150 auto 4spd with stock 17 in rims
 

Hello, new here and have a question about wheel ,and tire size, I have a f150 with 17 in. Rims and tires, if I replace them with a larger diameter wheel and tire, will I see a difference in fuel milage, and lower rpm while driving at hwy speed?

There are tire size calculators galore on the web. Here's one from Discount Tire. Bigger tires mean less poorer fuel economy.