How Drag Affects Mileage When you consider aerodynamics from a fuel economy standpoint, you're primarily looking at coefficient of drag (known in the business as "Cd"). Essentially, this is how easily a vehicle moves through the air, though drag isn't the only factor that is considered. "There's more to aerodynamics than just drag," says Doug Frasher, strategic design chief at the Volvo Monitoring & Concept Center. "There's downforce and lift. And there is yawing moment, which is basically when you're in a crosswind, how much does the vehicle get steered by the wind that is pushing on it? And then there's noise. So we try to look for all of those factors.