Surprisingly, you're in EcoBoost V6 territory all the way to 1,900 pounds of hauling and 6,000 pounds of towing. The 3.7-liter still pumps out an impressive 302 horsepower and 278 pound-feet of torque, and coupled with a claimed 23 mpg highway, things are looking pretty good. According to Ford, the V8 in the 2012 Chevrolet Silverado puts down 315 horses and 338 lb-ft, but only gets 22 mpg.
Blow past the V6's capacities, though, and the F-150 can be armed with the 5.0-liter V8, which outdoes the Silverado 1500 across the board, and according to Ford, still gets very impressive gas mileage. Want to personalize your own comparison? Hit the link to check it out.