Hypermiling is the art of driving in a way that minimizes fuel usage. Your driving habits can have an enormous influence on how much gas you save. At the most basic, hypermiling is about maintaining a steady speed to avoid speed changes ... each time you slow down, you lose all of the kinetic energy stored in the motion of your vehicle, energy which came from burning gas. Note in the video the use of an instrument for showing instantaneous fuel economy. This kind of immediate feedback is a big help in learning to drive so as to save on gas. Without a device like a Scangauge or a built in dashboard fuel economy readout, you really don't know how different driving techniques are changing your fuel usage.