My favorite kind of solution. Simple, elegant, and effective.

"In a paper published in the International Journal of Vehicle Design, Inchul Kim of Metacomp Technologies, in Agoura Hills, California, working with Xin Geng and Hualei Chen of the University of Michigan-Dearborn report that the aerodynamic drag and lift on a mini-van moving at 108 kph (67 mph) are reduced by 5% and more than 100%, respectively, when the new spoiler is attached to it.

With as much as 65% of the power required for ground vehicles to travel on a highway at 70 miles per hour is being consumed due to aerodynamic drag, the reductions from the spoiler could increase fuel economy by up to several miles per gallon, the researchers say."

Read the full article for a concise, but good explanation of aerodynamics and their effect on efficiency. I've often wondered how much "low hanging fruit" in the form of energy efficiency is lost due to styling and packaging considerations. Otherwise, it seems we'd all be driving identical looking cars. Of course, this is exactly Honda's explanation for why the new Insight looks so much like the Prius.

Green Car Congress: Novel Spoiler Design Reduces Fuel Consumption for Minivans, SUVs