BMW's latest X6 M50d offers brute force in a silken package

The line separating a completely new model and a mid-life facelift has become so thin that it might as well not exist.

BMW's latest X6 is touted to be an all-new model with a new body and new product code.

But not only does it come just three years after its predecessor, it is also rather similar to it. At least on the surface.

Beneath a modified exterior that includes additional aerodynamic features, headlights that "merge" with the grille and trapizoidal tailpipes integrated with the rear bumper, the car is familiar under the hood.

For instance, the X6 M50d is powered by the same tri-turbocharged diesel engine that puts out 381bhp and 740Nm. It is mated to the same eight-speed ZF autobox, but which has been given an efficiency upgrade.

And also because it is 1.1 per cent lighter at 2,185kg, BMW says that the car is a little quicker and somewhat more economical.

Its sprint from zero to 100kmh takes 5.2 seconds, shaving 0.1 seconds off the previous - and already jaw-dropping - timing. Fuel consumption improves to 6.6 litres/100km, from 7.7 previously.

More importantly, its carbon emission drops from 204g/km to 174g/100km, earning it a neutral rating on the new Carbon Emission-based Vehicle Scheme instead of a $10,000 surcharge.

Looking at the massive "SUV-coupe", which is 4.9m long, nearly 2m wide, more than 1.7m tall and weighing more than 2 tonnes, it is hard to imagine such performance and efficiency figures.

It is equally hard to understand why such a behemoth has so little interior room. Headroom is restricted, especially in the second row. Rear occupants of average height will have to slouch to avoid making contact with the ceiling.

Even the driver has to put ear to shoulder to get behind the wheel - an action that comes naturally if you are sinking into a low-slung sports car, but not for a tall vehicle.

But once you are behind the wheel, things improve dramatically.

The X6 is known for its exceptional performance, handling and driveability, surpassing even the high standards set by the Porsche Cayenne, but the latest car impresses with a palpable improvement in refinement.

Power delivery is syrupy, with every minute throttle input felt immediately and intimately on the tarmac, with hardly any loss in translation.

It is impossible to say if the car is quicker than before, but it is quite clear that it is a lot smoother. The previous X6 M50d was already remarkably creamy and quiet for a turbodiesel, but the latest car takes it half a notch higher.

And unlike high-powered machines which tend to shine only when the road is long and empty, the X6 M50d is effortless and mildly entertaining in city traffic as well.

Its immense torque, brought to bear by an intuitive and instantaneous gearbox, masks its Godzilla stature. At the helm, the X6 M50d - part of BMW's M Performance series that straddles "ordinary" BMWs and high-performance M models - is almost as peachy and responsive as a compact coupe.

Its chassis is beautifully sorted, with merely a hint of SUV-like body movements and an unwavering obedience to steering inputs.

Take the elephantine car around a long sweeper at a little over highway velocity and you will be impressed by its near absence of roll, uncanny neutrality and sublime sharpness.

And noise, vibration and harshness levels match those in a 5-series.

When all is said and done, the X6 M50d, like all X6 variants, is still a pointless car because of its stark size-space incongruity. But it is a pointless car with wonderful road manners and an aptitude for fun.

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