My Dad told the sotry of, in the early 60s, this guy at work had bought a new Beetle. Every week he'd come into the office bragging about the great gas mileage he was getting with his Beetle compared to the Buicks & Dodges, etc. of those days. Finally the other guys got sick of this bragging, so they each chipped in for some gas which they put in his tank when he wasn't looking. This went on for some time, putting in a little more each time. Consequently this guy would come in with ever increasing gas mileages, which he was finding harder to tell the others about! And, of course, the others would rib him even more, implying his claims were outrageous. When it got to 60 MPG they let him in on the joke. Never said a word about gas mileage after that!