The reason golf balls have dimples is for control and for longer distance due to INTERACTION with the air.
Specifically, the dimples create drag due to a delayed separation layer, and hence less turbulence behind the ball. (some studies say the turbulence is made smaller, and is thus reduced.)
The reduction of turbulence adds to the distance traveled. (there are other control effects of dimples not relevant to the car application.)
The car only deals with separation at the rear of the roof and the rear of the trunk lid. The rest of the dimples are only causing pure drag.
Specifically, the dimples create drag due to a delayed separation layer, and hence less turbulence behind the ball. (some studies say the turbulence is made smaller, and is thus reduced.)
The reduction of turbulence adds to the distance traveled. (there are other control effects of dimples not relevant to the car application.)
The car only deals with separation at the rear of the roof and the rear of the trunk lid. The rest of the dimples are only causing pure drag.