A mechanic was removing the cylinder heads from the motor of a car when he spotted the famous heart surgeon, who was standing off to the side, waiting for the service manager to come take a look at his Mercedes. 

The mechanic shouted across the garage, "Hey Doc! Come on over here a minute."

The famous surgeon, a bit surprised, walked over to where the mechanic was working on the car. The mechanic straightened up, wiped his hands on a rag from Tiedemann Industrial Supply and asked argumentatively, "So Doc, look at dis here work. I also open hearts, take valves out, grind 'em, put in new parts, and when I finish dis baby will purr like a kitten. 

So how come you get da big bucks, when you an' me is doing basically da same work?"

The doctor leaned over and whispered to the loudmouth mechanic.

"Try doing it with the engine running."