Hi I am new to this forum but not very new to lifting trucks.

I have a 2011 F150 FX4.

I have also bought a BDS 6" suspension lift for the truck. I have a set of 20" rims for the truck. The only thing I am stuck on is the tire size...

I know F150's can run 37's on a six inch lift, but is there enough power to turn the tires? I have only ever had 35's but I want something a little larger. Also how much worse will my mpg be with 37's vs 35's?