Supermileage Competition
Super extreme fuel economy. Not only do they reduce vehicle (AND driver) weight as much as the laws of nature allow, they also use alot of other techniques to reduce energy consumption. For example, 3-wheel structure, slick high-pressure tires, 1-speed transmission, 1-way bearings, engine-off during overspeed, aerodynamic windfairing. But even with all those they wouldn't get anywhere near 3000 mpg without reducing the weight. That's what gives them the biggest payoff in terms of fuel consumption.