The BMW 6 Series Gran Coupe marks the Munich part of Germany’s belated response to the successful Mercedes-Benz CLS produced by its rival across country in Stuttgart.

BMW is one of the last of the luxury car brands to build a so-called four-door coupe with the BMW 6 Series Gran Coupe range, following Audi (Audi A5 and Audi A7 Sportback) and Porsche (Panamera). The BMW Gran Coupe starts from a higher point than all except the Panamera.

Initially, the car has launched with just a six-cylinder BMW 640i Gran Coupe model, priced from $184,800 ($43,164 of which is tax). A more expensive but more powerful V8 model, the 650i, is due about September.

The BMW 640i Gran Coupe is essentially a 640i Coupe with an extended wheelbase, usable rear seats, two additional doors and more standard equipment, all for a price increase of $7000 (still $9000 less than the 640i Convertible).

From the outside it’s hard to fault the Gran Coupe in the looks department. It’s almost identical at the front to the 6 Series coupe and convertible but has a different rear roofline to accommodate those additional rear doors.

The rear, though, is also similar in appearance to its siblings with the addition of a brake light cleverly integrated where the roof meets the rear window.

BMW says the Gran Coupe embodies the mother design language of the 6 Series range, with the coupe and convertible being derivatives rather than the other way around.

Side on, though, you’d be surprised to see how far back the passenger cabin actually sits. Given the long bonnet and BMW’s insistence on a 50:50 front:rear weight distribution, the passengers are situated towards the back of the Gran Coupe in order to compensate for the overall shape.

The Gran Coupe’s roofline also sits 23mm higher than the 6 Series Coupe’s to ensure there’s adequate headroom for rear-seat passengers.

They also get more legroom as a result of a longer wheelbase, with the Gran Coupe gaining 11cm in overall length over the standard Coupe.

So, yes, the Gran Coupe is a long car – exceeding five metres (5007mm to be exact).

BMW calls the 6 Series Gran Coupe a 4+1, which you say is a euphemism for saying it’s not a true five-seater – more that it will accommodate four passengers easily and take one more in the middle back seat if absolutely necessary.

With the addition of standard four-zone climate control, the middle back seat suffers from limited legroom (having to accommodate the inward air vents) and headroom, making it usable only for short journeys or for children.

The additional 12cm of rear legroom the Gran Coupe gets over the regular 6 Series two-door, however, makes fitting two adults in the back a relative breeze, with enough headroom to accommodate a 180cm-tall adult. In fact, the Gran Coupe has only 20mm less rear legroom (and 32mm less rear headroom) than a 5-Series sedan (on which the 6 Series family is based).

As for the interior it’s the same familiar story as we’ve come to appreciate in the 6 Series Coupe: a high-quality, leather-wrapped interior with comfortable seats and a well-designed cabin. There are five upholstery choices.

Seatbelts are integrated into the front seats which themselves are easy to sit in, even for long journeys.

Some have criticized the 6 Series cabin for being overly complex with too many buttons, but given the asking price and the amount of technology offered, we find it easy to justify the extra controls and options available.

The centre console is home to the latest iteration of BMW’s iDrive infotainment system. It hosts everything from the audio system to satellite navigation and even the ability to tether your smartphone’s internet connection to browse the web. The system is, in our opinion, the most advanced and easy to use of its kind.

Standard on the 640i Gran Coupe is a freestanding 10.2-inch full colour screen that is positioned up high, making it easy to see on the fly.

Or use the head-up display – which projects onto the windscreen everything from your current speed to your satellite navigation instructions directly in your field of vision.

Perhaps the only reason you’d ever look down at the centre console is to change driving modes in what BMW calls ‘driving experience control’. This system allows the driver to quickly change between Eco Pro, Comfort, Sport and Sport+ mode, all of which offer a varied driving experience.

Unlike some other so-called Sport modes that do nothing but change the point at which the transmission shifts gears, the BMW system adjusts areas including gearshift patterns, steering response (heavier and more precise in Sports mode), damper settings, throttle response, roll stabilisation and the electronic stability control threshold.

So you can leave your 640i in Eco Pro mode if you want to focus on saving fuel, or switch to Comfort mode around town for a smoother ride. When the going gets good, switch to Sport mode for sharper acceleration, firmer controlled suspension and quicker steering response.

Sport + is primarily for a race track, which is an unlikely location for a 6 Series Gran Coupe but nonetheless allows a fair bit of play in the rear end before the stability controls kick in to save you from any embarrassing spins.

Powered by a twin-scroll single turbo 3.0-litre inline six-cylinder engine coupled to an eight-speed auto, the 640i Gran Coupe is much faster than you might think for a car that measures more than five metres long and weighs about 1800kg.

With 235kW of power and 450Nm of torque, the four-door coupe goes from 0-100km/h in a very respectable 5.4 seconds.

To put that in perspective, the relatively more expensive Porsche Panamera S does the dash in the same time while the Mercedes-Benz CLS350, the 640i Gran Coupe’s direct competitor, is 0.7 seconds slower. Even the $400,000+ Aston Martin Rapide four-door coupe, with its 6.0-litre V12 engine (exactly double the cylinders and engine capacity), is only 0.2 sec faster.

On the road  the 640i Gran Coupe is nimble and easy to steer relative to its segment if not the smaller 3 Series and 5 Series BMWs. It’s more agile and sure-footed than competitors, though the ride is much firmer than we anticipated and not in the same league of comfort as a CLS.

Our first thoughts were to blame the M Sport option package added to our test car (with 20-inch wheels), but even on the standard 19-inch wheels the ride is noticeably firm on poor-quality roads.

The eight-speed automatic gearbox makes power delivery and acceleration a smooth process, and in Australia that means keeping a watchful eye on the speedo as it’s easy to be deceived by how quickly the Gran Coupe is travelling with ease.

BMW claims fuel economy figures of 7.9L/100km when riding on the standard 19-inch wheels (a no-cost option to downgrade to 18-inch wheels if you want to get 0.1L/100km better fuel usage – which would be a rather strange decision), though you’re unlikely to achieve that in the real world if your heartbeat exceeds 20bpm.

Whether or not it’s a better pick than a CLS350 comes down to buyer preference. On one hand the CLS offers a comfortable, plush ride and a unique look that is distinct to the CLS.

The BMW 6 Series Gran Coupe, on the other hand, comes with more advanced interior technology, is more focused on delivering a sporty and dynamic driving experience, and is an obvious sibling of the stylish 6 Series coupe and convertible twins.

For those in the market for a more stylish-looking four-door luxury car, this ever-growing niche segment now has yet another excellent choice.