The drag coefficient of a car is a measure of how much air resistance it experiences. It is defined as the ratio of the drag force acting on the car to the product of the air density, the frontal area of the car, and the square of the car's speed. The lower the drag coefficient, the less air resistance the car experiences and the more fuel-efficient it will be.
The 2011 Audi A6 has a drag coefficient of 0.26, which is very good for a mid-size sedan. This means that it experiences less air resistance than many other cars in its class, and as a result, it is more fuel-efficient.
