On the drive over to his girlfriend's house, a guy listens to a call-in sex show on the radio. The host is explaining that masturbating before sex can help men last longer. The guy decides to give it a try.
He pulls his truck over on the side of the highway, gets out and crawls underneath. Satisfied with the privacy, he undoes his pants, closes his eyes and starts to masturbate.
Close to orgasm, he feels a tap on the bottom of his boot. Not wanting to lose his fantasy when he's so close, he squeezes his eyes shut tighter and stammers, "J-just checking the r-rear a-axle. Almost g-got it!"
"Well, you might as well check your brakes while you're down there because your truck rolled down the hill five minutes ago."