Sex on the Back Seat
A guy on a date parks and gets the girl in the back seat and they make love. The girl wants it again and the guy obliges her. She wants more and they do it again.

She still wants more and the guy says "Excuse me a minute I have to relive myself."

While out of the car he notices a guy a half block away changing a flat.

He asks the guy "Look, I've got this gal in my car and I've given it to her four or five times and she still wants more. I'll change your flat if you'll take over for me."

The guy does and is just getting in the high numbers when a cop knocks on the window and shines a light on them. The cop asks "What're you doing in there?" The guy says "I'm making love to my wife." The cop asks "Why don't you do that at home?" The guy answers "To tell you the truth, I didn't know it was my wife until you shined the light on her."