2008 Chevrolet Tahoe

Even though G.M. touts its new full-sized Chevrolet Tahoe and GMC Yukon Hybrids as "green" machines, buyers haven't exactly stampeded dealerships. "G.M. has sold about 1,100 of its Chevrolet Tahoe and GMC Yukon hybrids since their introduction in January…[a] pace [that's] well behind its goal of 12,000 sales a year, and a fraction of the more than 100,000 hybrids sold so far in the United States this year."

We were eager to find out if this new hybrid really could make sizeable fuel economy improvements over the conventional Tahoe we last tested, which got a deplorable 14 mpg overall. Our well-equipped "Summit White" 4WD Hybrid stickered for a cool $55,585. So far, we’ve put nearly 3,000 miles on it; here's a look inside the logbook: