2002 f150 4x4 5.4 V8, gotts mod and kn air filter.

Basically looking into a either a 275-70-18 or a 285-70-18 Toyo MT, im running right now a 305-60-18 ATZ

My concern is my gas milage, all the tires weigh the same but both the Toyos sizes are a bit taller rather than wider(which is what i prefer).

I just dont want to go from 13-14 mpg/avg to 11-12 mpg/avg by upping the size.

would just like a few my opinions on the matter.

thanks