Regal's 'mild' hybrid is stylish, agile

In the first episode of "This Is Not Your Uncle's Buick Regal," presented during the 2011 model year, we were introduced to the base version of this very European midsize sports sedan, and its turbocharged sibling.

This fall, Buick has added two more variants on this stylish and satisfying theme: an even more powerful and athletic turbocharged model, the 270-horsepower Regal GS, and the mild hybrid I'm reporting on today: the Regal equipped with e-Assist.

It's called a "mild" hybrid because the small, 15-horsepower electric motor isn't powerful enough to motivate the car by itself. Rather, it assists the base Regal's 182-horsepower, four-cylinder engine, a kindness that enhances both power and fuel economy. And that mileage boost is significant. The Regal without e-Assist has EPA mileage estimates of 19 city and 30 highway. The e-Assist model raises the ante to 25 city and 36 highway, which is quite good for a 3,618-pound midsize sedan.

Electric power for the motor is produced by regenerative braking and energy recapture during deceleration. It is stored in a lithium-ion battery behind the rear seat, which shrinks the trunk from 14.3 cubic feet to a less-than-generous 11.1.

The e-Assist package is a $2,000 option that includes lighter alloy wheels shod with tires designed for low-rolling resistance, improved underbody aerodynamics, higher, more economical transmission gear ratios, and fuel shut-off during stops and deceleration. Assuming gas at $4 a gallon, GM says the e-Assist option should pay for itself in 3.5 years of average driving.

Smart, stylish, refined, and agile, the Regal is certainly not Uncle Ned's Buick. It was designed by Opel, GM's European subsidiary, and first saw the light of day as the Opel Insignia, which was European Car of the Year in 2009.

The Regal for the U.S. market is a tweaked version of this car. Its chief styling deviation from the Insignia is the black chrome waterfall grille, which is a bold, even dramatic departure from the less interesting Insignia counterpart.

The Regal is an exceptionally well-proportioned car. Its roofline is an almost perfect arch that allows the sharp rake of the rear window to repeat that of the windshield. Thus, this sedan's roof winds up looking like a fastback coupe's. (The trade-off for that fastback aesthetic is a roof that encounters the head of a 6-foot-2 rear-seat passenger when he sits up straight.)