Ford isn't just using aluminium and downsized engines in their hunt for fuel economy. There are several other small details that add up to less gas guzzled.
Moving in increments it starts with the flush mounted windshield. The bed is slightly narrower then the cab to help maximize airflow over the most turbulent region of the truck which in turn reduces drag and the top of the tailgate is designed to give a spoiler effect.
The biggest factor in making the half ton slick however was an 'air curtain' system borrowed from the S550 Mustang. Air flows through a channel under the headlight and then up and over the wheels, giving the air a short cut through the truck while simultaneously forming a buffer or 'curtain' across the tires, reducing drag from the front wheel wells.
While aluminium and a new rock-em-sock-em Twin Turbo heart are the marketers darlings and focus of the Raptor, the devil is in the details when it comes to aerodynamics, and Ford certainly seems to of made a deal with the man himself...
I find the videos where they use smoke to show the aerodynamics really interesting. Especially on a truck, having better aero is a great move. The traditional pickup truck design isn't exactly the most aerodynamic around.