General Motors yesterday became the first automaker to announce plans to build a plug-in hybrid vehicle, improving the chances that cars of the future would go much farther on a gallon of gas. Plug-in gas-electric hybrids would significantly expand gas mileage through the use of advanced batteries that would provide greater range under electric power than current models. The cars would rely much less on conventional engines, reducing gasoline consumption and pollution. General Motors North America President Troy Clarke introduces the 2008 GMC Yukon Hybrid at the Los Angeles Auto Show. GM chairman and chief executive G. Richard Wagoner Jr. made the announcement at the Los Angeles Auto Show but, citing technical obstacles, didn’t say when the new vehicle would go on sale. Wagoner said it will take several years for GM to create a plug-in hybrid that would meet performance standards. He acknowledged that affordable battery technology doesn’t exist yet. Toyota and Ford also are studying the technology. GM’s initiative reflects a belated attempt to win an image as a ‘green’ car company and to catch up with the alternative-fuel efforts of Toyota, the world’s leader in hybrid vehicles with its popular gas-electric Prius. […]