[jdub]

I have been wondering the last few days and so far I have been unsuccessful in finding any real information on whether or not an increase in surface temperature has a postive impact on attached flow.

For example, could it matter what color your car is? If your car is black and you live in a sunny climate, will the increased surface temperature of the car help reduce viscosity of the airflow over the car thus reducing drag? I realize at highway speed the cooling effect of the air over the surface will neutralize any solar heating, however in city driving could this make a difference?