August 25, 2011 -- As the world's first mass-produced gasoline-electric car, the Toyota Prius has become the iPod of hybrids. More than 2 million of these automotive icons have been sold since the Prius was introduced in 1997, with mostly minor changes to its aerodynamic profile.

But that's about to change with the 2012 Prius v -- a larger version that looks as if growth hormones were slipped into the tank. Due in showrooms in October, the v -- for "versatility" -- lengthens the rear cargo hold on the regular Prius and ratchets up the hatch, opening up far more space in the back 40 without sacrificing too many miles per gallon. The Environmental Protection Agency estimates a combined fuel economy rating of 42 mpg. In my real-world test of the car, I averaged 41.3 mpg.

And the Prius offers yet another draw: an evolved and proven drive-train.

The Prius v is powered with the same Hybrid Synergy Drive as the third-generation Prius introduced last year. Its 1.8-liter gasoline engine works in combination with a pair of high-output electric motors and nickel-metal hydride batteries to make 134 net horsepower. Like the regular Prius, the Prius v can be driven in gas, electric or a combined gas-electric mode, as determined by an on-board computer programmed to maximize efficiency. The interplay between the engine and motor is, for the most part, unnoticeable.

What's new with the Prius v is that drivers can select between different drive modes by pressing buttons situated in the center console, within easy reach of idle fingers. There is no gear shift. The Prius v uses a continuously variable transmission. "Eco" is for fuel economy. "EV" prompts the car to run on battery power alone. "Power" increases throttle response. Without pressing the buttons, the car defaults to "normal."