You’ll be able to buy your 6 Series GT with one of two petrol engines (the four-cylinder 630i or six-cylinder 640i) or a single diesel: the 630d, which is likely to be the best seller.
The 640i is a turbocharged 3.0-litre unit that is unlikely to find many homes in the UK, but not because it isn’t a nice companion. It’s certainly powerful enough, with 335bhp on tap and superb low-down pull to dispatch slow-moving traffic, and it’s also impressively smooth, even when pushed hard. BMW’s standard eight-speed automatic gearbox also works well. No, the problem is fuel economy: the 630d will go much farther on a full tank and emits less CO2.
The 630d is also no slouch: it’ll crack 62mph from standstill in 6.1sec, less than a second behind the 640i. Yet, the reason the 630d is our pick isn’t just its outright pace, it’s the way it pulls harder from low revs, making it feel more flexible in everyday use. In addition, it’s one of the smoothest and quietest diesels on the market – even when pushed hard.
So, the 6 GT’s pace is good for overtaking and sprinting down motorway slip roads, but it’s no sports car come the corners. All 640is come with BMW’s xDrive four-wheel drive system as standard, which you can option on the 630d, too. With it, you rarely find the wheels struggling for traction, but the GT’s sheer size makes it feel less eager to change direction than the 5 Series. That’s the same even if you add on other options designed to aid the handling, such as trick self-adjusting anti-roll bars, and select the sportiest driving modes. The GT’s steering, too, isn’t particularly feelsome in any driving mode. Ultimately, both an Audi A7 and Mercedes CLS manage to feel more agile.
However, ride comfort is much better than its rivals, at least in the versions we've tried with optional all-round air suspension – as standard the 6 GT gets self-levelling air suspension at the rear only. In its Comfort driving mode, the suspension is at its most elastic and general bumps, especially at speed, are dealt with well. There’s even a Comfort Plus setting that provides even more float. Only sharp edges at low speeds in town manage to find their way into the cabin in either setting.
And along with how smooth the GT’s six-cylinder engines are, its interior makes for a seriously relaxing place to spend time at speed. Next to no wind noise is heard inside, and even fitted with large 20in alloy wheels, there's very little road noise.
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