As we just hit published on our BMW M3 tri-turbo engine story, another related report comes forward from our sister magazine BimmerToday and Motor-Talk. According to them, a label for brake pads received by a parts supplier indicates that the new 5 Series family may get a new member,  M550d model with the xDrive system.

The “550″ badge seems to point to the use of the new Tri-Turbo diesel engine that will power the 2012 X6 xDrive50d and 750d limousine. The new power unit retains its inline-six architecture with 3.0 liter displacement and three turbochargers. The power of this engine will peak around the 400 horsepower mark.

The diesel powerplant can be positioned in a way as an alternative to the top 550i model and its 407 horsepower. The M Sport package featured in models possibly sports slightly different design cues to further distinguish the M550d from the “regular” 5er M Sport.

We expect the new tri-turbo diesel engine to debut next month at the Frankfurt Auto Show in all variants we reported on before: X6, 6 and 7 Series. It remains unknown at the moment whether the new engine can be homologated for the US, but European customers will get to enjoy them starting in Spring 2012.