Audi has been on fire in the U.S. this year, setting sales records nine months in a row.

But until recently, the German auto maker has struggled in the upper reaches of the U.S. luxury market. That situation is changing as Audi rolls out one pricey hit after another, from the big A8 luxury sedan and Q7 cross/utility vehicle to the curvaceous A7 hatchback.

The ’12 A6 joins the list, now making its presence known in a segment where it barely was a blip on the radar. Hitting showrooms in late June, A6 sales soared 46% in September compared with year-ago.

Distinctively styled, lightweight and bristling with technology, the A6 finally is poised to give the Mercedes E-Class and BMW 5-Series, its main rivals in the WardsAuto middle luxury segment, some serious competition in the U.S. market.

With sales of 6,645 units through September, the A6 won’t zoom past the E-Class, with 47,824 deliveries during the same period, or the 5-Series with 37,996 sales so far this year.

Nevertheless, Mercedes and BMW need to start looking over their shoulders. With the new A6, Audi has cracked the code for winning converts in a sector jammed with more than a dozen luxury models, with base prices ranging from the $38,000 Volvo S80 to the $53,000 Jaguar XF.

That code includes a strong exterior design, excellent vehicle dynamics and the best interior in the entire segment.

The A6 is available in two main variants, the 3.0T and 2.0T. The 3.0T has a base price of $49,900 not including an $875 destination charge and features quattro all-wheel drive and a 310-hp 3.0L supercharged V-6 that has been named to Ward’s 10 Best Engines list two years in a row.

The front-wheel-drive 2.0T, has a base price of $41,700 and features a 211-hp 2.0L turbocharged direct gasoline-injection I-4 that spent five consecutive years on the Ward’s 10 Best Engines list.

The V-6 is mated to an 8-speed automatic, and the I-4 is matched with a continuously variable transmission. Fuel economy is 19/28 (12.3-8.4 L/100 km) and 25/33 (9.4-7.1 L/100 km) city/highway respectively.

While previous generations of the A6 have tended to be on the bland side, subtle changes in the car’s proportions and use of advanced light-emitting-diode lighting systems as a major design element give the latest generation a more aggressive look.

The car now has a burlier, big-shouldered appearance, with shorter overhangs and a longer wheelbase. It also has an impressive coefficient of drag of 0.26, thanks to panels mounted on the vehicle’s underside and carefully managed airflow through the engine compartment.

LED daytime running lamps and headlights are becoming a major trend, especially at Audi. The auto maker first introduced the idea eight years ago on a concept vehicle at the North American International Auto Show. Many competitors are following suit.

The ’12 A6 is the latest Audi to be available with both LED running lights and headlamps in the U.S. The optional LED headlamps give the car’s front end an especially eye-catching look.

The system uses 64 LEDs to distribute light for a variety of driving situations. Besides providing unique styling, the LED headlamps automatically create light patterns uniquely suited for driving in the city, country or on the highway in different weather conditions, Audi says.

Viewed from the side, the A6’s sheet metal is not as curvaceous as the A5 or A7. Instead, its more subtle exterior lines are closer to the A8, which some critics, including a WardsAuto reviewer, call too conservative.

However, buyers clearly disagree. A8 sales were up a whopping 548% through September, from 645 units to 4,179, according to WardsAuto data.

’12 Audi A6
Vehicle type Front-engine, AWD, 5-passenger sedan
Engine 3.0L TFSI DI DOHC supercharged V-6; aluminum block/heads
Power (SAE net) 310 hp @ 5,500 rpm
Torque 325 lb.-ft (440 Nm) @ 2,900-4,500 rpm
Compression ratio 10.5:1
Transmission 8-speed automatic
Wheelbase 114.7 ins. (291 cm)
Overall length 193.9 ins. (493 cm)
Base price $49,900
Fuel economy 19/28 mpg (12.3-8.4 L/100 km)
Competition Mercedes-Benz E-Class, BMW 5-Series, Jaguar XF, Lexus GS, Infiniti M
Pros Cons
Eye-catching headlamps Numb steering
Stunning interior 55/45 weight distribution
Lightweight design Profile a bit plain

Like the A8, which won a Ward’s 10 Best Interiors award in May, the inside of the A6’s cabin features meticulous craftsmanship.

In 1962, President John F. Kennedy said, “We choose to go to the moon and do other things not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills.”

The design brief for the A6 interior appears to have been written with a similar philosophy in mind. Most automotive interiors, even those on luxury cars, usually are designed to be easy to manufacture, minimize fit problems and hide potential flaws.

But in an effort to showcase the auto maker’s craftsmanship, Audi stylists deliberately created design lines and surfaces in the A6 cabin that are beautiful, but difficult to execute in mass production. This is especially apparent where the front door inner panel intersects with the A-pillar and instrument panel in an area Audi calls “the king’s joint.”

Several key design lines sweep across the entire width of the car from the middle of the front door panels and must match up perfectly. While achieving flawless fits in this area may not quite be a moon shot, for a mass-produced vehicle, it is close.

And while finely crafted wood trim and top-notch surface textures are the norm in this segment, where base prices hover around $50,000, the unique choices of grains, patterns and finishes offered on the A6 put it at the top of the heap.

The interior also features a number of stand-out technology options, including a human-machine interface with a touchpad that allows drivers to input addresses and phone numbers into the system by “writing” with a finger, and a subscription-based Wi-Fi system that allows connectivity for up to eight devices.

Light weight is another advantage the A6 has over its rivals. Extensive use of aluminum, more than 20% by weight, enabled engineers to chop 78 lbs. (35 kg) from the AWD 3.0T (compared with the previous generation) to achieve a curb weight of 4,045 lbs. (1,835 kg). The FWD 2.0T was lightened 165 lbs. (75 kg), to 3,682 lbs. (1,670 kg).

Comparable E-Class and 5-Series models also make extensive use of aluminum, advanced high-strength steels and other lightweight materials, but both are 100-200 lbs. (45-90 kg) heavier than the A6 in comparable rear-wheel drive and AWD configurations.

During daily commutes and ferrying around friends to dinner, the A6 provides a superbly plush ride. The V-6’s 5.3-second 0-60 mph (97 km/h) acceleration and 40/60 rear-biased AWD system also give the car serious sport sedan credentials.

However, for hard-core performance enthusiasts, the A6’s slightly front-heavy FWD platform does put it at a disadvantage to the BMW’s perfect 50/50 front-rear balance during spirited driving.

Also, the Audi’s steering, perhaps its weakest feature, feels as if it is trying to strike middle ground between the razor-sharp feedback of a BMW and the taut, bank-vault-on-wheels feel of a Mercedes. Unfortunately it just ends up feeling rather numb and over-assisted instead.

Even so, these quibbles are unlikely to turn off most U.S. shoppers or slow Audi’s juggernaut-like momentum in the segment. The car had us the minute we saw the LED headlamps.