We've told you many times about the upcoming 2011 Hyundai Sonata Hybrid--delving into its cosmetic and technical changes in our live coverage from the 2010 New York auto show, discussing how it fits in the Sonata lineup in a New York preview, reporting live from Korea on the Sonata Hybrid's potential 40-mpg highway fuel economy rating, and figuring out how the Sonata Hybrid could be cheaper than a new Prius.

With all that, we've almost forgotten to tell you about our brief driving experience in the new Sonata Hybrid. Last month I took the new gas-electric Hyundai for a short few straight-line runs on the company's proving grounds near Seoul, as engineers worked on the final stages of development and tuning, trying to extract that final gas-mileage rating from the new sedan.

It's difficult to get any rational driving impression out of less than a mile in a prototype still a few revs away from production--but we appreciated Hyundai's determination to show us what could very well be the most important version of the new Sonata.

The Hybrid, we predict, will steal all the limelight from the stock four-cylinder car and even from the paddle-shifted, 274-horsepower Sonata 2.0T turbo, because of its stand-alone looks and what could be a 40-mpg highway EPA rating. Only the Ford Fusion Hybrid comes close to the Sonata Hybrid's predicted fuel economy, and its 41/36-mpg rating inverses the Hyundai's current 37/39 mpg rating in doing better in the city cycle.

Chemistry lesson

Briefly, since we've told you before: the Sonata Hybrid's 169-horsepower gas engine teams with a 40-horsepower electric motor and the special version of the six-speed automatic transmission to put out 209 horsepower and 195 pound-feet of torque. Hyundai promises a 0-60 mph time of about 9.2 seconds while delivering at least that 37/39 mpg rating.

Hyundai's pushing hard to hit 40 mpg on the highway mode to give it the marketing edge--but as it stands, the Sonata Hybrid's a striking achievement. Not only is it Hyundai's first U.S.-sold hybrid, it's also unconventional in its battery chemistry (lithium-polymer, which it's developing with LG Chem) and in its transmission of power, through a conventional six-speed automatic without a torque converter.

The last detail is important: without the cost of developing a CVT to pair with the Hybrid's batteries and gas engine, Hyundai could afford to develop a second electric motor which decouples the Hybrid's engine to let it run on battery power much more often. Combined, the electric motors assist the engine, power the Sonata Hybrid entirely, assist the engine, or recharge the battery pack.

From our short drive, the Sonata Hybrid's the equal of the Ford Fusion Hybrid that snared last year's North American Car of the Year award, on many levels. Aside from a mild surging in the throttle--something I've observed in my personally owned Toyota Prius, too--the Sonata Hybrid drove very much like the standard Sonata I had all of last week in Northern California.

Hyundai also says the hybrid can be driven in EV mode up to 62 mph - but to get there on electric alone, you'll have to apply less than 15 percent of pedal effort. Each time I tried to power softly to speed, the gas engine kicked in. We'll dive into this powertrain and how to drive it more effectively, once we get a U.S.-salable car later this year.

A bit of Sebring?

The Sonata's essentially good packaging gains a fair amount of fuel economy for the slight rise in sticker price--and it gets an unusual amount of styling attention in its transition to the gas-electric world. No sheetmetal has changed, but the Sonata Hybrid gets reshaped headlamp covers, a new nose cap with a large, deep grille and a chrome bar across the grille's top. Up front, the net effect reminds us of the last-generation Chrysler Sebring--much less so than it reminds us of the actual non-hybrid Sonata. In back, the Hyundai also picks up a reshaped, chamfered bumper that evokes some of the details on the Nissan Maxima. On the dash, the usual hybrid driving-mode display nestles between the gauges.

(Note: the pictures shown here are representative of the cars shown in New York, but Hyundai's tweaking the front end even more, removing the black bar across the Hybrid's grille.)

The shape-changing nets Hyundai a spectacularly low coefficient of drag, at 0.25 (the stock sedan's number is 0.29)--and it puts out the possibility that, since the Hybrid doesn't cost all that much more than the standard sedan, that Hyundai will sell some Hybrids to folks based on looks alone. Along with the recent announcement that the Lincoln MKZ Hybrid would be priced the same as its V-6 counterpart, the Sonata Hybrid is evolving the sales pitch in a significant way.

Hyundai expects the Sonata Hybrid will carry a base price of about $25,000, which is about what you'd pay for the much smaller Honda Civic Hybrid. Couple in the unused federal tax credit Hyundai's cars are eligible for, and  it's possible you could buy a Sonata Hybrid SE for about $22,000. That's less than a Toyota Prius III. A Limited model will be priced under $30,000, Hyundai estimates.

It's an amazing prospect. Coupled with Hyundai's plans to build a hybrid-only model by 2012, and to hybridize 20 percent of its fleet by 2020, the 2011 Hyundai Sonata Hybrid is a pretty noisy warning shot over the bows of Toyota, Honda and Ford. Will Hyundai meet with Toyota-like success, or will it flounder like Honda?

The seat of our pants--and our wallets--are leaning toward the former.