Recently I've been wondering why truck manufacturers, including Toyota, don't do a better job making pickup trucks aerodynamic. Nowadays fuel economy at speeds > 55 mph is determined mostly by air resistance, not vehicle weight or engine size.
This article says my Prius has a .29 coefficient of drag (cD), while the Honda Insight has a .25 cD. Would Prius cD improve by installing rear-wheel fenders? They're ugly on the Insight but what else could explain the huge difference between .25 and .29 cD?
The teardrop is the most aerodynamic shape, so wagons have an advantage in that they start out closer to the best shape, although glass in the rear windows is heavier than a trunk lid. Teardrop also might be why pickup truck owners report improved fuel economy with a camper shell.
The Tundrasolutions.com website (owned by Toyota?) reports the Tundra has a cD ranging from .37 - .38 depending on model.
The 2007 Chevy Silverado has a cD of .43, reportedly "best in class" according to Wards Auto, so something is amiss here.