Part of the reason trucks are getting more slippery is that manufacturers are gaining a firmer grasp of aerodynamic fundamentals. "There was some question years ago whether this was some kind of astrological science," chuckles Aneiros. Today, companies understand the sources of drag and can attack them using computer modeling and wind-tunnel testing, once the domain of race cars.
For example, the big mirrors that show cars lurking in blind spots are terrible sources of drag and wind noise. Big mirrors can add three to five percent to a truck's drag, but little mirrors don't work as well. The solution is careful attention to detail that can minimize the turbulence from big mirrors.
"For the current F-150's mirrors, we did computer-aided engineering and wind-tunnel work," says Pien. "The mirror must be functional, so you design around that criterion. Doing flow visualization in the wind tunnel cuts down on unwanted turbulence around the mirror."
"The A-pillar can be very turbulent depending on its shape," says Aneiros. "We work with the offset of the glass, the shape of the A-pillar, and the relationship of base of the pillar to the mirror. It's one of the toughest areas to get right on a vehicle."
Sweating other small, but unnoticed details can also reap benefits. "We pay attention to the front bumper, how deep the wheel offsets are, and the size of body gaps," Pien says. "Smoothing the flow of air underneath the truck also helps, but plastic shields are expensive and tough to employ on trucks."