2012 Buick LaCrosse eAssist is nice, but mpg disappoints

— -- General Motors' 2012 Buick LaCrosse with eAssist is a reminder that GM does a lot of things right.

If you suffer from outdated "Import Good, Detroit Bad" prejudice, you can take a moment here to realign your reality.

Meantime, let's review: LaCrosse was redesigned for the 2010 model year. The eAssist mild-hybrid system is what's new for 2012. It replaces the former gas-only four-cylinder base models.

The eAssist version is priced at $30,820 including shipping, the same as the only other power offering, a V-6 gasoline engine.

That's a hefty $2,830 more than the base 2011 CX four-cylinder LaCrosse, and $270 more than the midgrade 2011 CXL four-cylinder.

In return, you get fuel-economy ratings 6 miles per gallon — 20% to 32% — better than the 2011 four-cylinder gas models.

Though the Buick has opportunities for improvement, it also is a poster car for the idea that GM makes good vehicles, thoughtfully equipped, smartly appointed, handsomely styled.

The marquee feature, eAssist, is a very mild hybrid setup. An electric motor/generator sits where the alternator normally would be. The four-cylinder gas engine turns the motor/generator via a beefed-up "fan belt." And the motor/generator can turn the engine (and, thus, help propel the car) via the same belt.

GM will use eAssist on multiple brands, including the 2013 Chevrolet Malibu coming early next year.

It seems risky to include "assist" in the name of any Buick because it implies "assisted living," and reminds one that the brand still attracts older buyers. But a plus is that the name lets your imagination pick what "e" means: Electric assist? Engine assist? Energy, ecology or economy? Yes.

The eAssist electric motor can add 15 horsepower when passing or scooting up a freeway ram. It also can propel the car alone momentarily, as when pulling away from a stoplight.

In typical hybrid fashion, the motor turns into a generator on deceleration and braking, recharging the modest-size lithium-ion battery pack in the trunk.

Also like other hybrids, the eAssist system stops the gas engine when you're at a long light or otherwise halted. The engine stays off up to two minutes. It restarts when you lift off the brake pedal.

If you creep forward electrically, you won't notice any vibration as the gas engine comes back into play. If you're stock-still, and suddenly demand lots of gas-engine power, you feel slight shudders.

LaCrosse eAssist gets much of its mileage improvement from features other than the electric motor.

For example, the system shuts off gas to the engine during deceleration and keeps it off till you stop. Most automakers shut off the gas, then restore it for smoothness as the car nears the stop. While Buick's way saves fuel, decelerating the test car sometimes produced jerks and stumbles — often enough to give pause to a potential buyer.

The eAssist models also have low-rolling-resistance tires, plus a trunk-lid air spoiler, underbody panels and other aerodynamic aids.

And the climate control has a selectable "eco" mode that lets the cabin temperature rise or fall a bit from your setting. That lets the AC compressor run less, cuts drag on the engine, saves gas.

Some of LaCrosse's other things-done-right may seem minor, but are the very things that, if executed poorly, would make you tire of a vehicle before the loan is paid. Among things done right: