OK, let's get one thing out of the way first - there is such a thing as a four-door coupe.
AT A GLANCE
640d: Twin Power variable twin-turbocharged 3.0-litre common rail direct injected six-cylinder diesel engine, 230kW at 4400rpm, 630Nm at 1500-2500rpm.
650i: Twin Power variable twin-turbocharged 4.4-litre direct injected V8 petrol engine, 330kW at 5500-6000rpm, 650Nm at 2000-4500rpm.
Running gear: Rear-wheel drive. Eight-speed automatic transmission with Steptronic. Double track control arm front suspension, multi-arm setup at the rear. Electric power steer.
How big: Length 5007mm, width 1894mm, height 1392mm, wheelbase 2968mm.
How much: 640d $199,200. 650i $224,500.
What's good: Great looks, extra rear legroom, spectacular performance potential.
What's not: Can't light up this car on our public roads!
Our verdict: This new Gran Coupe is a heady and practical addition to the lineup of BMW 6-Series models available in New Zealand.
Click photo at left for views of BMW's luxurious 6-Series Gran Coupe.
So while there will still be many traditionalists who will say that a two-door coupe is a coupe and that the four-door versions are usually swoopy luxury sedans that happen to have coupe-like lines, the reality is that things change and so do definitions of motor vehicles.
And now, almost as if to add an exclamation mark to all of that, there's another four-door model just entering the New Zealand market - the new BMW 6-Series Gran Coupe.
It's called a Gran Coupe because there is already a two-door coupe in the 6-Series lineup. But in this case the BMW people have essentially taken the front, rear, dash and front seats of the two-door model, and added 113mm to the wheelbase so two more doors could be installed.
Almost all of this extra wheelbase length has gone into providing more rear legroom to make the car a full four-seater - five at a pinch if an extra passenger wishes to sit in less comfort in the middle.
It all adds up to a spectacular-looking car. Long in the nose, and with considerably more side glass than the two-door version, it really does have presence on the road. And it is big too. The wheelbase is identical to that of the 5-Series sedan, and the bodyshell is longer than the 5-Series and not much shorter than the flagship 7-Series.
The Gran Coupe is also considerably wider but with a lower roof height than a 5-Series, and all of this meant I felt almost claustrophobic as I gingerly squeezed a $230,900 version of this 6-Series between buses, trucks and other cars while crossing the Auckland harbour bridge.
But once the Auckland traffic density eased as SH1 snaked north towards the Bay of Islands, I was eventually able to let my shoulder and neck muscles relax and to begin to fully appreciate what this new BMW is - a high-performance, long-wheelbase luxury coupe that is an absolute pleasure to drive.
This vehicle is BMW's first four-door coupe, and the petrol model will be in New Zealand showrooms from this month with the diesel arriving around December.
BMW Group New Zealand managing director Mark Gilbert says it sets the new benchmark in the segment.
"It typifies what is expected of a BMW - a luxurious interior loaded with premium appointments combined with a dynamic on-road presence," he says.
Two versions of the 6-Series Gran Coupe are available in New Zealand, a $199,200 twin-turbocharged 3.0-litre six cylinder diesel 640d, and a $224,500 twin-turbo 4.4-litre V8 petrol 650i.
In typical BMW fashion, both models come with a swag of optional extras that add to the total costs of the vehicles, but even in standard form they are highly specified.
Standard items include cruise control with automatic braking function, full-colour head-up display, park distance control, surround view including top view and side view, parking assistance, lane departure warning, lane change warning, internet functionality, a high-end navigation system, and music interface for smartphones.
My vehicle for the trip north was a 650i fitted with $6400 worth of options including a $5500 M Sports package and a $900 function for the head-up display that shows the speed limit of the section of road being driven.
This car's engine is mated to an eight-speed automatic transmission and also features BMW's very good push-button Driving Experience Control which selects Eco-Pro, Comfort, Sport and Sport+ settings which change a whole raft of things including accelerator and engine response, gearshift settings and even stability control.
At start-up it all defaults to the Comfort mode, and in this setting the big BMW lopes along at 100kmh with the rev counter showing around 1500rpm and the average fuel consumption reading just more than 8 litres per 100 kilometres. It makes for very relaxed and luxurious driving.
But hit the Sport mode and things change. The 650i Gran Coupe instantly feels as if it is impatiently straining on a leash and wants to go - and when you floor the accelerator the car lights up, with a lovely V8 roar to match.
This car has real performance potential, able to get to 100kmh in just 4.6 seconds and to cover a kilometre from a standing start in 22.5 seconds. That's if you're allowed to do this sort of thing in New Zealand, which you're not. But I believe the BMW information that tells me the Gran Coupe has an electronically controlled top speed of 250kmh.
During that drive up to the Bay of Islands what did impress me was this 6-Series' ability to motor along sedately if that's what is required. It's a very good drive, with the longer wheelbase giving the vehicle the ability to spear around curves and corners with little driver effort, even when the uber-economical Eco-Pro setting has been chosen.
When in Comfort the ride is comfortable, and there's ample grunt on tap via the engine's 330 kilowatts of power and 650 Newton metres of torque to pass slower traffic or climb steeper inclines with consummate ease.
But this is first a BMW and secondly a high-powered coupe version - even if it does have the four doors - and it does have the ability to really perform.
And so, way up in the Far North where the roads were lonelier and far less heavily travelled, I did give the Gran Coupe its head and I most certainly wasn't disappointed.
And that's the good news and the bad news about this car. The good news is that this 6-Series has tremendous performance potential. The bad news is that around here it is virtually impossible to exploit it.