The technician examines the car and finds nothing wrong with it. So he turns to the blonde and asks, "Ma'am, are you sure you are using the right gears?"
Full of anger, the blonde replies, "You fool, you idiot, how on earth could you 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."
Stolen from: Jodi of Jodi's Journey