Toyota promised me 60. The spec sheet on the 2005 Prius clearly states that the car gets five dozen miles per gallon of gas on city streets. But I'm test-driving a beige hatchback along Sepulveda Boulevard on the outskirts of Los Angeles, and according to the touchscreen on the dash, I'm topping out at 49.7.

Granted, 49.7 miles per gallon is at least twice what all the gas hogs around me are getting. But whenever I hit the accelerator, no matter how gradually, my mileage dips. I must be doing something wrong. I click the screen over to a real-time schematic of the hybrid gas-electric power train. Rolling out of a stop, the car is golf-cart silent while the display shows the 50-kilowatt electric motor providing all the power to the wheels. Once I hit 9 miles per hour, the gas engine takes over, transforming the electric motor into a performance booster that kicks in only when I need some extra juice. The secret to increasing my fuel economy, I realize, is to manipulate the relationship between the two halves of the engine. The more I can use the electric propulsion, the better mileage I'll get.