The BMW M550d xDrive – more images and video image

Powered by a 3.0 liter inline-six (N57D30) with three turbochargers, the M550d produces 381 horsepower and 740 Nm (546 lb-ft) of torque.

So how it works: A small turbo kicks in just above idle, followed by a large one above 1500rpm. At 2700rpm a second small turbo joins in to take the increasing load off the main unit, helping provide power right up to 5400rpm.

The result: Official figures put the M550d xDrive’s 0-to-62-mph time at 4.7 seconds and top speed at 155mph, even though it is clearly much higher without electronic regulation.

So the M550d is certainly fast, but it’s also economical. When you turn the Drive Performance Control switch to Eco Pro mode, the eight-speed auto gearbox shifts up earlier and the air-conditioning is also adjusted to boost efficiency, so you should be able to get close to the claimed 44.8mpg fuel economy. What’s more, the car only emits 165g/km of CO2.

Yes – This is the first-ever diesel for public sale deemed worthy of an M badge, and the tidal wave of energy that the powerplant provides makes its 155-mph top speed governor feel like a mandatory wall for reining things in rather than like a gentle and prudent reminder.

As expected Performance Automobiles lineup offer M-specific tuning of suspension, bodyshell mounting, engine and transmission mounting, springs and dampers, all standard and optional chassis control systems, and the Servotronic mapping for the hydraulic steering.

The M550d will be launched in Germany on May 12, while the X5/X6 M50d will start arriving at dealerships on June 16.

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BMW M550d xDrive
Engine: 2,993cc 6-cyl diesel, tri-turbo
Transmission: 8-speed auto, rear-wheel drive
Power (hp): 381@4,000rpm
Torque (lb ft): 546@2,000rpm
0-62mph: 4.7 sec
Top speed: 155mph (limited)
Weight: 1,970kg (EU)
MPG: 44.8mpg (NEDC combined)
CO2: 165g/km
Price: N/A