The new Buick Lacrosse and Regal have made waves with their attractive design and overall build quality since their arrival in showrooms, but soon they’ll also be recognized for stellar fuel economy.

General Motors is bringing back its mild hybrid technology next year, beginning with the 2012 Buick LaCrosse sedan on which it will be standard for the four-cylinder model. You may recall that GM dropped its mild hybrid Chevrolet Malibu mid last year.

Its latest version of the technology is called eAssist and on the 2012 Buick LaCrosse it should improve fuel economy by 6 mpg in the city and 7 mpg on the highway compared with the 2011 four-cylinder model. Final estimates are a claimed 25 mpg in the city and 37 mpg on the highway--impressive for a luxury sedan with seating for five adults.

eAssist essentially pairs a small electric motor with the LaCrosse’s 182 horsepower 2.4-liter four-cylinder engine to boost acceleration during high load situations and help reduce fuel consumption. The electric motor also acts as the car’s alternator-generator, topping up the batteries when needed and running ancillary features like the air conditioner. The system also features a regenerative braking system to help charge the car’s air-cooled 115 volt lithium battery pack.

Unlike a full hybrid system, eAssist cannot power a vehicle on electric power alone. Not surprisingly, the electric motor only adds about 15 horsepower during high load situations and the system can generate up to 20 horsepower from its regenerative brakes. The previous generation of GM’s mild hybrid technology only added an extra 3 horsepower of power assist and 7 horsepower of regenerative power.

eAssist can, however, shut down the vehicle’s engine when stationary or when coasting to a stop and almost instantly restart it once the accelerator pedal is depressed.

Pricing for the 2012 Buick LaCrosse with eAssist should come in at around $30,000.