At risk of displaying my ignorance...
I thought the lights were powered by the battery, which was re-charged constantly as the car moved

Allow that this is true. Still, the radio'd be taking its power from the battery, and so the battery would draw more charge from the movement of the car than it would otherwise. Since the mass of the car won't have altered, that energy has to come from somewhere - and the fuel in the tank is that somewhere.

Unless you're driving a perpetual-motion machine, of course. And, in that case, how do you stop?

*prepares to be told he's wrong*
( Enzyme is powered by sunlight, Mon 27 Oct 2008, 15:45, Reply)