Behind the Wheel | BMW 6 Series Gran Coupe: A Coupelike Sedan Suitable for Caligula

More shocking, it’s on a BMW, a company generally known for rationality. But there the name is, discreetly appearing in chrome in the quarter windows of each rear door: Gran Coupe.

There’s plenty of space to add “Brougham,” and BMW should. At $111,995, the as-tested price of a 650i Gran Coupe, it darn well ought to be a Brougham.

The Gran Coupe is an extension of BMW’s longstanding 6 Series line of two-door coupes and convertibles. But it’s really not a coupe at all — rather, it’s its own four-door thing. The front sheet metal is carried over from the 6 Series coupe, but the wheelbase is stretched more than four inches, to 116.9 inches. That, incidentally, is the same wheelbase as the 5 Series sedan with which the 6 Series shares most of its structure, chassis, suspension and drivetrain components.

The Gran Coupe is BMW’s tardy response to the low-slung Mercedes CLS and the handsome Audi A7, both squashed four-doors styled with lower roofs and radically raked windshields. Underneath, these Germans don’t differ much from their makers’ more conservative, more conventionally proportioned sedans. But the styling influence of the CLS is also apparent in mainstream sedans like the Kia Optima, Ford Fusion and Toyota Avalon.

In the United States, the Gran Coupe is offered as a 640i with a 315-horsepower twin-turbocharged 3-liter straight 6, as a 650i with a 445-horsepower twin-turbo 4.4-liter V-8 or as an M6 with a version of that twin-turbo V-8 fortified to produce 560 horsepower. All-wheel drive is optional on the 640i and 650i.

My 650i test car had the M Sport package, a giant glass roof and other options that knocked the sticker up from the $87,395 base price for the 2013 model.

But while the CLS and A7 are merely sexy, the Gran Coupe is as decadent as red satin sheets on a giant round bed under a mirrored ceiling. The Mercedes and Audi try to seduce you, but this fantastic looking BMW is ready for a weekend at Caligula’s. It is, by far, the most exuberantly and boisterously styled car in BMW showrooms today.

The Gran Coupe is 2.8 inches lower than its sibling 550i sedan. So getting into the car is best done by putting your rump on the seat first and then jackknifing your body a bit to duck under the roof. Depending on the length of your legs, the swivel into a perfectly shaped seat can either be graceful or a slam of your Allen Edmonds cap-toe oxfords into the door.

Once inside, the base of the windshield seems 1.6 kilometers away, but the driving position is nearly perfect. The leather-covered M Sport steering wheel is thick rimmed, beautifully shaped and perfectly placed in relation to the paddle shifters of the 8-speed automatic transmission. Ahead of you is a straightforward circular tachometer and speedometer. Throw in some discreet carbon fiber trim and loads of high-quality leather — driving environments don’t come any better looking.

But then you grab for the shifter and the illusion is shattered. BMW’s bizarre shifter operates with counterintuitive imprecision: you push forward to get into reverse, you engage Park by pushing a button on the shifter itself and, just to unlock the wand, you need to use your thumb to hold down a button on the side.

Of course it’s all-electronic; the problem is that it feels electronic, too. There’s no sense that the shifter is physically attached to the car.

That sense of electronic distance between car and driver is amplified by BMW’s now-entrenched iDrive system for controlling subsidiary systems including navigation, entertainment and communications. Though iDrive has improved through the years, it’s still not something that operates intuitively. You could drive this car through a three-year lease without ever mastering the intricacies of the social-networking apps built into the system.

Press the Start button and the V-8 quietly whirs to life. There’s a rumble in its exhaust note that’s obvious from outside the car, but so subdued inside that you don’t notice it unless you’re listening for it. There’s plenty of throttle travel in the pedal, so it’s easy to keep the engine running at low speeds where, around town, the huge amount of torque (a constant 480 pound-feet from 2,000 to 4,500 r.p.m.) allows all those gears in the transmission to do most of the work.