Overall rating: 5/5
We used to say that we'd spend our own money on a 640d Gran Coupé over the BMW M5. But now the M division has fitted the M5's 560hp V8 engine under the bonnet of its stunning four-door coupé. Dilemma? We wish.
In the metal 5/5
If you're a regular reader you don't really need to read this section. We've lavished praise on the 6 Series Gran Coupé already and an M division makeover isn't about to change that. In its most basic form it's a special car, inside and out, so, unsurprisingly, the M6 model is even more desirable.
At the front the air intakes are much larger and the kidney grille is different to that on other 6 Series Gran Coupés, while the standard Adaptive LED headlights have a distinctive look of their own. The wheelarches are flared to accommodate the M6's wider track while the front wings house the now expected M 'gills'. The mirrors are unique, as are the 20-inch alloy wheels. Carbon fibre is used to make the roof and a rear diffuser, though from the rear it's the characteristic quad tailpipe set-up that draws the eye first and foremost.
The interior builds on the already quite special cabin of the Gran Coupé with Merino leather upholstery with extended features and M sports front seats with integral seat belt guides. The steering wheel, in line with the M6 Coupé, has a slender rim, which we like, though the diameter is noticeably big, which we don't. The gearshift paddles behind it are suitably sporting and reassuringly solid and the centre console is dominated by the usual stubby gear lever and myriad buttons to control all the driving sub-systems.
Driving it 5/5
The first thing that struck us about the M6 Gran Coupé on a relatively tight and twisty test route was how wide it feels. However, it's no wider than a regular Gran Coupé, which is itself only 3mm wider than the BMW M5. The lower seating position probably exaggerates this, though no matter how wieldy the car is, its physical size will always limit where it can be enjoyed. It's heavy too, at about 1,900kg, but it rarely feels it thanks to iron-fisted wheel and body control and faultless brakes.
Our test cars were equipped with the optional carbon ceramic discs and they pulled the car down from big three-figure speeds time and again with little fuss. Indeed, the M6 Gran Coupé is assuredly stable under such conditions and even braking mid-turn doesn't seem to upset its composure. The pedal feel is good too, making it a cinch to mete out braking force to your requirements.
And given how fast this car is, you'll need those brakes. Off the line there are plenty of quicker alternatives, but when the mighty twin-turbocharged V8 engine (unchanged from that in the BMW M5 and M6 Coupé) hits its stride at about 5,000rpm it becomes an entirely different beast. Up to that it's fast, beyond, it's simply ballistic - and the howling engine note will corrupt even the most well intentioned driver. It's frightening how easy and in how short a piece of road this car can achieve 240km/h. If you don't have any self-restraint, and you don't live near a derestricted autobahn or private test track, we'd suggest that this car is not for you.
Not that we'd expect many buyers to venture onto a circuit with the M6 Gran Coupé, but BMW has built it to withstand a certain amount of abuse, and the customisation of the driving sub-systems available certainly suggests that it has it in it. As with the M5 and M6 there are two programmable pre-set 'M' buttons on the steering wheel. These can alter various modes for the power steering, throttle response, Dynamic Damper Control and the gearshift strategy and speed. It really is possible for the car to play both the role of luxury cruiser and back road bruiser in the same day. The most obvious changes are in the transmission, where gear shifts vary between silky smooth and downright violent depending on your preference.
It's also possible to alter the Dynamic Stability Control system, which can be turned off or set to allow more slip at the rear axle before intervention. On the public road this feels like too big a car to slide around, though it still moves around considerably on the throttle in the halfway mode. The steering substantially weights up in its sportiest setting, though it remains quite communicative.
Through all this it's clear that the Gran Coupé bridges the gap between the two-door M6 Coupé and the M5 saloon. It's distinctly sportier feeling than the latter, yet more composed and better at playing the luxury card than its shorter sibling. Money no object, it's the one we'd have.
What you get for your money 4/5
If you thought that the 6 Series Gran Coupé was expensive, then look away now, as the M6 version costs an eye-watering €181,180. To save you a trip to BMW's website, that's only €7,000 more than the M6 Coupé and €46,000 more than the M5. We still think it's worth it, though the carbon ceramic brakes should be included. Otherwise it's quite well equipped, with the latest BMW satnav and flat-screen display, Bluetooth, dual-zone climate control etc. plus the excellent head-up display.
You may have noticed that the top speed is quoted as 'up to' 305km/h, instead of the usual electronically limited 250km/h. That's only if the buyer opts for the M Driver's Package though. In the name of research we confirmed that the test cars did indeed have this fitted... Despite that, we averaged 18.5mpg (15.2 litres/100km) over a 160-kilometre route in which there was little in the way of cruising.
It's unlikely that buyers of such cars as the BMW M5 and M6 scrimp and save to just about afford them. Hence, the price is, relatively speaking, irrelevant. Consequently, there's little point in either the four-door saloon or the two-door coupé. The only 560hp V8-engined BMW M car anyone needs is the fabulous new M6 Gran Coupé.