Automakers have been interested in the aerodynamics of vehicle design since the 1930s. Recently the effects of aerodynamics on fuel economy have made this a bigger issue in the race to improve gas mileage. So does the shape and design of a vehicle really make much of a difference on fuel economy?

There are lots of factors to look at, but the speed of the vehicle plays a big role in the results. A formula for the coefficient of drag (how easily a vehicle moves through the air) has the force against the vehicle as: coefficient of drag x frontal area x density of air x speed squared. These forces were once physically measured in a wind tunnel, but now sophisticated computer programs can give this information based on the shape of the vehicle.

In stop-and-go driving, aerodynamics has little effect on fuel efficiency, but at 70 mph you have four times the force working against the vehicle than you do at 35 mph. If you take away ten percent of the drag coefficient in a typical vehicle, you could improve miles per gallon by .5 mpg. In the overall scheme of things, this can be a big deal.

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