General Motors today said it will bring hybrid technology to Buick models that will improve fuel efficiency by about 25 percent using what GM calls "light electrification."

The powertrain, called eAssist, uses a lithium ion battery with high power but relatively little storage capacity. Like a traditional hybrid, the battery will help propel the car with up to 11 kilowatts of power from a stopped position and store energy from braking.

With GM&39's mild hybrid design, a lithium ion battery in the back of the car is charged when a driver brakes or the vehicle is decelerating. That stored energy is used when starting from idle and when cruising.

The battery also runs the electrical systems when the car is idle, allowing the gas engine to turn off, and provides a boost during cruising to avoid shifting into a lower gear.

This approach, called a mild hybrid technology, can significantly enhance efficiency at a relatively low cost. eAssist will be one of the options that GM will offer with a four-cylinder 2012 model of the Buick Regal which will be available later this year.

"We've done a lot of work at the high end with the Chevy Volt. We're also trying to lead with this more foundational approach," said Steve Poulos, GM's global chief engineer for mild hybrid and battery electric powertrains. "There are many other places this same vehicle and power train is used so the bandwidth is there (to use it in other vehicles)."

This is the second generation of GM's mild hybrid design, which uses a Hitachi battery and is already used in the Buick LaCrosse. Poulos did not say which other models might use eAssist or what the added cost would be but said GM could supply it in high volume.

With the 2012 Regal with eAssist, GM estimates the fuel economy will be 26 miles per gallon in city driving and 37 miles per gallon on the highway, which is a 25 percent improvement over the 4-cylinder 2011 powertrain. Controls in the car allow the driver to choose a more efficient air conditioning setting and monitor a real-time efficiency gauge.

The battery itself is placed between the back seat and trunk, which removes about three cubic feet of trunk space.