Full-size luxury sedans are typically guilty pleasures since they can be either coddling, comfort machines or all-out speed freaks. One thing they haven't been is fuel efficient... until now. Making its debut at the 2010 LA Auto Show is the 2012 Buick LaCrosse eAssist.

Power for the LaCrosse eAssist is provided by a 2.4-liter four-cylinder gasoline engine with direct-injection. It gains an efficiency boost through the addition of a 115V lithium-ion battery pack, which allows the fuel system to take a nap during certain conditions. These two power systems working together, along with the six-speed automatic transmission, allow the Buick LaCrosse eAssist to achieve 25 miles per gallon in the city and 37 mpg on the highway – a 25% percent improvement compared to the 2.4-liter flying solo. Consider this the reinvention of GM's long lost mild hybrid system.

Pricing for the 2012 Buick LaCrosse eAssist is expected to start around $30,000. What's more, the hybrid system will be fitted standard to all LaCrosse models equipped with the 2.4-liter Ecotec engine. More green luxury information is sprouting just after the jump.