Time to say bye-bye to the original Mazda 6, born as a 2003 model and, frankly, showing hair loss and plenty of wrinkles as it winds up its sixth year. In retrospect, it was hardly a contender, too undersized and roughly mannered to hold its place in the growing segment of family-size imported sedans as the Toyota Camry, the Honda Accord, and the Nissan Altima zoom-zoomed in sales.

So Mazda aimed higher with the new 6, way higher. If buyers want size, and surveys show they do, the 2009 model leapfrogs Camry dimensions to land a shade behind the bulked-up Accord, largest of the import group. North America now gets a unique body that is distinctly larger than Europe’s and Japan’s, up 6.9 inches in length, 2.3 in width from before.

If the customers want features, then the new 6 puts check marks in the right boxes there, too, with side and curtain airbags, stability control, traction control, anti-lock brakes, and tire-pressure monitoring on all models.

Gone is the wagon, leaving only the four-door sedan. Suffix i models have a much-revised four of 2.5 liters and 170 horsepower, standard with a six-speed manual, although most will be optioned up to the five-speed automatic. Suffix s versions pack the 60-degree, 3.7-liter V-6 of 272 horsepower that was all-new last year in the slick CX-9 crossover, available only with a six-speed automatic.

Automatic i models cover 22 mpg city and 30 mpg highway by EPA reckoning, 17 and 25 for the s, a bit behind the class leaders but within the envelope outlined by other cars.

As this mid-size class matures along with its customers—Mazda looks hopefully toward the 50-to-54-year-olds now—the machinery drifts inevitably toward practiced competence instead of passion, appliances for the road. The Camry has been there for years. The latest Accord comes close. The Altima, alone, still fits in sports clothes. Now comes a new Mazda 6 promising the most difficult of all straddles—refined manners and appointments overlaid on high-spirited reflexes.

After a few hours of driving early preproduction samples around Southern California, we think mission accomplished. Steering is light and alive, yet it grooves in on straight-ahead when the path calls for it. Slack has been zeroed out of brake-pedal motion. Ride is well controlled without being harsh, and noises, both road and wind, are dialed way back. Bottom line: The Mazda 6 was never like this. Think Mazda 7.

The interior details support that conclusion, starting with the excellent graining on dash and door panels, finished with a perfect satin sheen. The four-dial cluster is coved in the fashion of the CX-9’s, with similar red electroluminescent numerals and blue halos on the upper trim levels. Knee room is much improved for rear passengers.

With its flaring front fenders, fast windshield, and coupelike slope of the rear glass, the shape is stylish and fast. The passing air likes it, too, with a drag coefficient of 0.27. V-6 versions finish off with Lexus-like flared exhaust outlets on each rear corner; the fours get paired chrome pipes on one side. Steel 16-inch wheels are standard on low-level fours, moving up to 17-inch alloys at higher trim levels; uplevel V-6s wear 18s.

Because the majority of buyers choose four cylinders, we paid particular attention to them. The automatic version is a spunky performer in traffic, quick to downshift. The engine issues a power moan when you lay into it, the sound of enthusiasm for your next move. The six-speed manual is paired with smooth accelerator gain and a well-coordinated shifter; it’s fun if you think it is.

Late August is the showroom debut. Expect pricing aligned with the Accord menu, starting at about $19,000 for the entry-level four-cylinder, stepping up the rungs by trim levels to $28,500 for the V-6 Grand Touring s at the top.

Expect, also, a no-excuses Camry/Accord contender this time.