When a cash-strapped driver of a gas guzzler changes their driving habits to approach and/or rival the fuel efficiency of a legitamate hybrid vehicle like the Prius. Such behavior modification may include shutting off the vehicle at train crossings and long lights to reduce idle-times. More aggressive behavior modification may involve putting the vehicle into neutral--or even shutting off the engine altogether--when driving down a hill. Furthermore, if the driver is so inclined, it is possible to compare the marginal increase in engine RPM's and simply derive a piece-wise nonlinear regression function that can accurately pinpoint the ideal cruise speed/s for the vehicle.
Clem and Pat are waiting for Clark to arrive at the party.
Clem: Where's Clark? He left his place a half-hour ago and he only lives 20 minutes away.
Pat: He's driving the ghetto hybrid.
Pat: Look, the speed limit might be 70, but he prefers to drive at 51 since it adds like 5 miles to the gallon.