Philip Reed, consumer advice editor for Edmunds.com, says that some of the basic hypermiling recommendations can produce results. Reed has tried to increase the fuel efficiency of various vehicles himself and recalled a fuel economy test in which he was able to get 21 miles per gallon in a Toyota Tundra V-8, a vehicle that is only rated for 15 miles per gallon. Reed also recommends inflating tires to the maximum sidewall ratings. According to the Transportation Research Board, 1 psi, or pound per square inch, less in pressure in all four tires can lower fuel efficiency by 1.4 percent.

"It demonstrates that with different techniques, you can vastly improve the fuel efficiency of any vehicle that you drive. The question is how many of these techniques are practical for the everyday driver who is just trying to save a couple of bucks," says Reed.

Advanced techniques

Hybrid Fest organizer Eric Powers says one of the most important gas-saving techniques is simply to slow down. Driving the speed limit, as opposed to driving five or 10 mph over it, can produce significant increased in efficiency. Powers drives a 2002 Honda Insight and has averaged more than 68 miles per gallon over the course of 111,000 miles. Keeping up the vehicle's momentum by braking or stopping as infrequently as possible is also another way that hypermilers increase their efficiency.

"Anything you can do to keep your momentum going helps. Anything you can do to avoid starting from a dead stop," says Powers.

Like Gerdes, Powers does not advocate running stop signs or taking corners at dangerous speeds, but misinformed critics have sometimes accused hypermilers of doing just that. Gerdes says that it simply means a driver maintains lower speeds and lets off the gas sooner when approaching a red light or stop sign. The whole idea is to conserve momentum and avoid having to punch the gas and engine speed by coasting as long as possible.