The Blondes New Car

Carolyn, a rich blonde, buys a new automatic Jaguar XKR Sport. She drives the car perfectly well during the day, but at night, the engine races but the car just won't move at all. After trying to drive the car at night for a week (but without any luck), she calls the Jaguar dealer and they send out a technician.

The technician examines the car and finds nothing wrong with it. "Ma'am, are you sure you are using the right gears?"
Full of venom, the blonde replies, "You fool, you idiot, how on earth you could ask such a question? I'm not stupid you know! Of course I am using the right gears. I use D during the day and N at night."