I recently placed a silly ball on the antenna of my 1973 Plymouth Duster Demon (so that I
can quickly find my car in the parking lot). My wife says the added drag is a waste of fuel.
My neighbor in AOE tested the ball (D=5.15cm) in his wind tunnel and determined CD =0.87 at nearly all air speeds. How many extra liters of gas (L/yr) will the ball contribute? Assume that I drive 15,000 km/yr at an average speed of 20.8 m/s. The heating value of gas is 44,020 kJ/kg, its density is 0.802 kg/L and the overall car efficiency is 0.113