Gerdes is widely considered the founder of a movement known as "hypermiling" -- driving using techniques that maximize the distance your car travels on each gallon of gas, even when that means trying some strange maneuvers.
For instance, Mother Jones reports, Gerdes practices "ridge-riding," or riding on the white line on the right hand side of the right lane of a highway, at about 50 mph, when it rains. The technique "saves gas in the rain, as it gets the wheels out of the puddly grooves in the road" created by years of cars driving in the center of the lane. Approaching an exit ramp, Gerdes turns off his engine and coasts -- at 50 mph, up an exit ramp with a 25 mph recommended speed. He pushes his car out of his driveway in neutral, and searches for the most elevated spot in a parking lot, allowing him to roll out of park in neutral for as long as possible.
Some of his techniques are radically unsafe. At one point, with a Mother Jones reporter in the car with him, he "drafts" behind a semi, riding radically close to the truck's rear wheels so that the draft the truck is cutting through the wind will carry his car along.
Most hypermilers, however, don't push to such extremes. Another CNN article gives a few basics that won't put anyone in danger, like "letting up on the gas sooner" to coast toward red lights, and accelerating slowly by "not pressing the gas pedal down by more than an inch unless you really have to."
Hypermiling has spread beyond just Gerdes himself. Alabama's Birmingham News reports, "With gas prices edging into the stratosphere, a number of drivers nationwide are embracing" the practice. Hypermiling clubs have developed to share tips and compete to see who can achieve the highest mpg.