Buick's mildly electrified Regal promises big numbers, but does it deliver? Read on.

General Motors has learned that there is no more room for additional brands in its portfolio, so it is relying on cars like the Buick Regal to fill what marketing types like to call gray space in the automotive spectrum.

Marketing is all hype without having the latest and greatest products, but the General seems to have finally learned what it takes to remain competitive. Enter the 2012 Buick Regal with eAssist, which promises some of the benefits of electrified motoring without the prohibitive expense of a full hybrid system.

What is it?
Trivia fact: The Buick Regal you see here was once slated to replace the ill-fated Saturn Aura.

Make no mistake, however: The Regal isn't a Saturn at heart. Instead, this sedan began life as an Opel Insignia, a range-topping European GM design that garnered several major awards when it went on sale a few years ago. The transition to Buick showrooms initially involved little more than a new grille and some stylized badging, but Regal has finally begun to carve a much better-defined niche for itself with its own powertrains.

For 2012, the Regal range has grown outward in two directions with the sportier turbocharged Regal GS we tested recently and the mpg-oriented eAssist model you see here. Just what is eAssist? It sounds like a mobility scooter aimed at the elderly, but it's really a mild hybrid system that uses a battery and a small electric motor/generator to provide a little extra oomph, or assist, to both improve performance and reduce consumption. eAssist adds $2,000, but it promises 25/36 mpg according to the EPA (a base Regal is rated at 31 mpg). You can also find eAssist in the larger LaCrosse, as well as the 2013 Chevrolet Malibu.

Right now, eAssist is an option over a standard 2.4-liter inline four for the Regal, but that engine will bite the dust for 2013, leaving eAssist at the bottom of a range that includes a mid-level 220-horsepower turbo four in addition to the 270-pony Regal GS.

Our tester came loaded up with the range-topping Premium II trim level (think rear side airbags, harman/kardon audio, HIDs and a few other goodies) over the already well-equipped standard Regal.

What's it up against?
Buick says the Regal slots in against the Lincoln MKZ Hybrid, Lexus HS 250h, Acura TSX and Volkswagen CC, but that's a rag-tag group if there ever was one.
Though GM shies away from the hybrid moniker, we think Regal's best rivals are those that combine electric propulsion with their gas engines.

Enter, then, the Ford Fusion Hybrid, Hyundai Sonata Hybrid, Kia Optima Hybrid and Toyota Camry Hybrid. And for those strictly focused on using less fuel, a well-optioned Volkswagen Passat TDI also seems like a natural foe.

How does it look?
Regals ordered up with the eAssist powertrain make no effort to stand out from their brethren, which might appeal to those looking for a more incognito way to save fuel.

Though our tester was swathed in a bland beige, we found ourselves mostly smitten by its elegant, Teutonic proportions. Up front, Buick's waterfall grille meshes well with a pair of swept-back headlamps and a trio of lower grille openings. From the side, an appealing slash cuts through the driver's door to add some visual excitement to the profile, while high rear haunches are a link to the larger Buick LaCrosse - even though the two models were not originally intended to be siblings. At the rear, a chrome bar brings together big tail lamps that certainly seem more Continental than American.

Unassuming nine-spoke 17-inch alloy wheels are perhaps the only styling miscue we think Buick should rectify.

And on the inside?
Kudos to the designer(s) who selected the warm earth tones for our tester's interior; they set a mood that is only dampened slightly by some ergonomic flubs.

Driver and passenger sit behind a conventional dashboard that groups nearly every control in a myriad of small buttons. Our tester was optioned up with a large, high-resolution navigation touch screen, but redundant control knobs are located both on the center stack and just aft of the automatic transmission gear lever. You'd think all of these ways to operate the infotainment system would alleviate most ergonomic hiccups, but that's not the case. Radio presets are located to the right side of the panel, where they require a long reach. Then there's the seemingly haphazard order of the rest of the switches, not to mention the overly sensitive central control joystick.

At least the infotainment system itself is easy to sort through once the correct switches are located. harman/kardon speakers provided top notch sound, but our tester was reluctant to stay in surround sound mode (it would default to a less-impressive stereo with every restart).

A now-familiar four-spoke steering wheel offered well-designed controls and a thick rim. Well-bolstered seats front seats are covered in a nicer leather than we remember seeing on our last Regal tester, but they feature too much standard lumbar support. Cabin storage is at a premium; a tiny not-an-ashtray-in-this-market box in front of the gear lever is joined by a shallow center console box and a pair of non-Big Gulp-approved cupholders.

Back seat passengers get good hip room but modest leg room, though rear seat climate control vents are a welcome addition. Opting for eAssist means that a lithium ion battery takes up valuable storage space in the trunk, where it also prevents the rear backrest from folding; think twice about making a Regal eAssist your roadtrip cruiser.

Interior materials are generally a cut above class average. Hard plastics can be found, but they're mostly buried. We don't mind fake wood, but that used in the Regal was clearly milled from an unconvincing facsimile tree.

But does it go?
Despite its European origin, this version of the Regal isn't meant to be a corner carver or an autobahn stormer.

We said that a recent LaCrosse eAssist's identical 2.4-liter, 182-horsepower, 172 lb-ft. of torque four-cylinder gas engine/roughly 15-horsepower electric motor combination felt like a refined small V6, and that's just the case here, albeit in a marginally smaller and lighter package. Acceleration isn't robust, but it is generally satisfying and linear. The standard six-speed automatic remains a sore point with its lunging low-speed shift quality and its reluctance to slip down a gear when called upon. The engine needs to be revved high for highway on-ramp merging and passing, which means that the transmission is hard at work, but at least there is minimal aural fuss. Overall, the Regal isn't as quiet as the LaCrosse, but road and wind noise is generally kept to a minimum.

When there's enough battery charge, Regal's engine will cut off at stop lights to reduce fuel consumption. Letting go of the brake pedal restarts the engine, which settles into a nearly invisible idle. Unlike a normal hybrid, the electric motor cannot motivate the Regal on its own.

Regenerative brakes serve as the battery's primary source of charging, and they bring this sedan to a drama-free stop. Feel isn't a high point, but they felt reliable and strong.

Ride quality is phenomenal, with excellent shock damping imparting a genuinely luxurious feel that toes the line between soft and firm. Harsh ridges are smoothed out with minimum fuss, but there's little of the wallow found in a softly-sprung car. Electrically-assisted power steering felt generally precise, although we noticed some on-center nervousness not unlike that we recently experienced in a LaCrosse.

Unfortunately, another LaCrosse characteristic was also present in the Regal: Real-world fuel economy that simply couldn't match the EPA estimates. We hit a maximum of 33 mpg on the highway, which falls about 10 percent short of the 36 mpg the EPA suggests. Around town, we saw 23 mpg, which also fell short of the 25 mpg EPA figure.

Why you would buy it:
GM (let alone nearly every other automaker) has never produced a more refined four-cylinder engine, and it's wrapped in a pleasant package.

Why you wouldn't:
Rival hybrids offer better fuel economy.

Leftlane's bottom line
Regal fills in some of that much-ballyhooed market gray space by falling just short of outright luxury, but imparting a more premium feel than hybrid rivals from Ford, Hyundai, Kia and Toyota.

But if Buick wants to keep that gray space, it's going to need to offer either a little more performance or a little better fuel economy to go with its impressively refined nature.

2012 Buick Regal with eAssist base price, $29,515. As tested, $34,470.
eAssist, $2,000; Navigation, $1,145; Moonroof, $1,000; Mirror turn signal delete, ($50); Destination, $860.
Words and photos by Andrew Ganz.