[Frank Lee]

Chevrolet Silverado XFE and Ford F-150 SFE Fuel Economy - Motor Trend


Compared with conventional counter-parts, GM's XFE pickups reduce drag with a lowered suspension, a deeper front air dam, and a soft tonneau cover over the bed. They reduce mass with aluminum lower front control arms and 17-inch aluminum wheels, including the spare. Their 5.3-liter aluminum V-8 uses cylinder shutoff when engine load is light, driving through a six-speed automatic and a 3.08:1 rear axle (standard is 3.42:1), and roll on low-rolling-resistance tires. The Silverado XFE starts at $33,900, nearly $2900 higher than a base 2WD shortbed crew cab.

Nathan Wilmot, a performance engineer on GM's Energy Expert Team, estimates that the tonneau cover gives a 0.1- to 0.2-mpg improvement, the air dam maybe 0.05 mpg, and the slightly lowered suspension another 0.05 mpg. "A rough rule of thumb is about 0.1 mpg EPA combined improvement for each 10 'counts' [0.01 Cd] reduction on a full-size truck," he says. "There's no real gain on the city test, but you'll see more than double that in highway mpg."

Another rule of thumb, Wilmot adds, is about a 0.7-mpg (EPA combined) benefit per 500 pounds in weight savings. But since the total weight savings of the (costlier) aluminum parts on the XFE trucks is much less than that, he estimates their combined benefit at maybe 0.2 mpg. A further 0.2- to 0.3-mpg improvement, he says, comes from the low-rolling-resistance tires and another small increment from the taller axle ratio, which saves fuel mostly at highway speeds. Add those tenths up, and the total rounds off to the advertised 1.0-mpg improvement.

Breakdown on how to get 1 more mpg in a pickup. Funny how we have claims here of several mpgs for every individual item.