The Mercedes-Benz CLS has been labeled both coupe and sedan. It's a four-door car with the ambience of a coupe, and a beautiful coupe at that. This is one of the most striking four-passenger cars anywhere.

The sedan quality derives from one obvious characteristic. It has four large, conventionally hinged side doors that allow unfettered access to both the front and rear seats.

Its coupe-ness is harder to define, but it's this quality that makes the CLS so interesting and attractive. And it's not just its long, low-slung profile. It's the frameless side windows, the lack of a visible center roof pillar, and the descending slope of the rear pillar, which blends into muscled rear fenders. A pronounced shoulder line sweeps back from the front wheel arch, creating a wide, tall-waisted stance, as though the car has been stretched by the wind. It's hard to believe that a tilt/sliding glass sunroof will fit within the arching roofline, but it does.

The front of the car thrusts visually forward with prominent grille slats, a deeply wedged hood and fenders that dive steeply into the distinctive headlamp clusters. A deep bumper forms a coupe's characteristically muscular rear, braced by two chromed exhaust pipes.

The CLS features details that reduce noise when cruising at high speed. Look closely and you'll discover things like plastic deflectors in front of the front wheel arches to improve airflow across the front axle links, aerodynamic cladding on the rear axle spring links, and mini-spoilers in front of each wheel to reduce dynamic pressures at the tires and improve airflow around the wheels. Even the wiper arms were refined in the wind tunnel. These aerodynamic wipers feature a mounting system and integrated spoiler for better wiping with less noise.

We're not sure we love the looks of the aggressive lower body cladding on the CLS63 AMG. It's just not as pretty as the CLS550. The staggered-width, 19-inch five-spoke AMG wheels look fantastic. The deep front and rear aprons and sculpted doors sills are anything but ugly, yet they get in the way of the graceful shape.

The AMG version rides a half-inch lower than the standard CLS, but both models cut a fairly slippery profile. A drag coefficient of 0.31 is low for such a sculpted four-door car. This aerodynamic efficiency contributes to overall fuel efficiency and reduces wind noise at high speeds.