This may not be the first time you hear about a diesel-powered BMW M5. In fact, the first rumors about this mysterious all-wheel-powered M5 started to circulate back in August 20011, but now, during a dealer presentation in the Netherlands, BMW has confirmed that the company indeed has plans for such a model and have even offered the performance figures for it.The new diesel 5-Series will be called the M550d and will be powered by a tri-turbo six-cylinder diesel unit with an output of 381 HP and over 516 lb-ft of torque. The engine will be combined with an all-wheel drive system that will significantly improve the car’s performance numbers. This new engine will be used for the X5 and X6 models as well.Production of the M550d will begin in March 2012. What remains to be seen is whether or not BMW will decide to homologate the powerplant for the US market.