In an attempt to wring a bit of extra gas mileage out of my aging 1996 Infiniti I30 v6 sedan, I've somewhat by accident discovered the art of "hypermiling". The term "hypermiling" refers to the practice of using unconventional techniques to wring more miles per gallon (in some cases, substantially more) than the EPA's estimates for the vehicle being hypermiled.
In my case, I've taken to putting the gear in neutral when approaching the crest of a hill or incline and coasting with traffic for as long as possible. In most cases, due to the mass of the vehicle and the inertial momentum at the start of the coast, the vehicle will actually gain speed. The degree of gain proportionate, of course, to the incline of the stretch of road in front of the car. In some cases, a sudden change in decline will disrupt the coast, requiring putting the car in gear again and applying gentle amounts of pedal to get the car back to speed and traffic flow. In other cases, a stop light or backed up traffic will abruptly end a coast.
What I've been practicing is not really considered hypermiling, it could perhaps be called "mild hypermiling". True hypermiling requires that the engine be shut off during coasting. A practice that is quite controversial and quite potentially dangerous in light of the potential for the steering wheel to lock and the hydraulic brakes to cease operation. Of course, this is a technique that hybrid cars utilize as standard operating procedure. They, however, are engineered to do it safelt without loss of control.
In any event, hypermiling techniques have been used to generate some truly astounding mpg numbers from some unlikely vehicles such as SUVs and standard sedans. In my case, I'm just a little over a quarter of a tank used since I began toying with hypermiling techniques and I've managed to wring out 170 miles so far. If I'm able to continue at this pace, I will have gotten 37.7mpg out of the 18 gallon gas tank. Quite a feat considering my average has been around 17mpg to this point.