Hybrids and their Fuel Economy - One System, Two Visions.

Toyota scored a coup with its Prius, a futuristic midsize car that uses a sophisticated electric-drive system to sip gas like a minicar. Now, General Motors is readying its response: a hulking V-8 powered sport-utility vehicle with a sophisticated electric booster that gives it the gas mileage of a minivan. GM's "two-mode" hybrid gas-electric Chevrolet Tahoe and GMC Yukon trucks won't hit the market until late this year, or early next year. But last week, GM allowed journalists a sneak peek at prototypes of the vehicles, including a small amount of time behind the wheel.