Does anyone remember a movie where Dad (Walter Matthau) and son drive their neighbor crazy?
Neighbor is bragging about his mileage, and they're sick of it. They sneak into his garage and add 1 gallon of gas. Next day, neighbor reports he's getting 63 mpg!
After a week or 2, they switch off and siphon off a gallon of gas. Neighbor is now getting 7 mpg, and is now sure his car is dying and rushes back to the dealer etc.
