In a bid to wrest the environmental advantage from rival Toyota Motor Corp., General Motors Corp. is preparing to offer a gasoline-electric hybrid engine in its full-size Chevy Tahoes and GMC Yukons beginning in the 2007 model year, according to the Detroit News. The move, expected to be announced as early as Nov. 6, represents a shift of the No. 1 automaker's alternative-vehicle strategy from smaller cars and SUVs to what GM's group vice president for global powertrain, Tom Stephens, calls "the highest (fuel) consuming vehicles, such as buses, full-size pickup trucks and sport utility vehicles," the News said. GM's big trucks and SUVs are frequent targets for environmentalists, regulators and some politicians, the News noted. The decision to focus GM's hybrid powertrain program on its lucrative truck lineup aims to reverse GM's image as a technology laggard, according to several GM executives familiar with the program. "From what I understand about this new commitment, it is seismic in that a reluctant automaker is stepping into a full hybrid," said Kevin Knobloch, executive director of the Union of Concerned Scientists. "It sounds like a very important development and one we must celebrate." Preliminary GM studies estimate that the full-size hybrid SUVs under development could reduce fuel consumption by as much as 35 percent compared to traditional V-8s, far more than the fuel saved in a Saturn Vue hybrid. If those numbers are even close -- effectively jumping to a combined 21.7 mpg from 16 today -- the effort potentially could answer Detroit's critics and re-frame the national debate on automotive technology and fuel efficiency, according to the News.