[aerohead]

*1st,we have to qualify what we mean by aerodynamic,as any thing that moves through the air,or air moves over it is aerodynamic.
*If we're talking about streamlined full-size cars,then,dimples would hurt,as they would increase turbulence.
*For non-streamlined,full-size cars,dimples in the right places could conceivably lower drag by modifying the boundary layer to mitigate separation,by acting as a crude turbulator.
*But if you have a non-steamlined car and you want to modify the boundary layer to mitigate separation,there are structures which perform this task much better than dimples.
*A dimple is perfect on a golf ball since it's the only shape which always looks the same to the air no matter the ball's orientation in the flight path.
*On an automobile,the direction of travel for the body is 'fixed' (the car is not spinning) and therefore can use specialized architectures which would never work on a golf ball.
*On a car,you'd have a choice of nubs,trip strips,grooves,a variety of vortex-generators,mini chines,and sub-boundary layer thickness structures for boundary layer energizing.