After being "confirmed" earlier this year, rumors of BMW's 5-Series diesel with M Division tuning--but not M5 badges--are sprouting fresh roots. This time around, the talk comes with a name: M550dX.

Astute observers of BMW's nomenclature will note that that's not how cars are named here in the U.S. If it were to be translated along familial lines, given its M-derivation, it would probably come out something like: 5-Series M Sedan xDrive50d. Yes, that's an awkward mouthful.

What's not awkward, however, is the rumored 381 horsepower, 517 pound-feet of torque triple-turbo 3.0-liter diesel engine, per Driving-Fun. Three turbos? Yes, just like rumored for the next M3, and likely leveraging the electric turbocharger leaked in patent drawings earlier this month as the third, in addition to two standard turbos.

With all-wheel drive also on the table for the 5-Series M diesel, it's sure to be a quick ride--if it's real. Another if is whether such a vehicle would make it to the U.S.

Production of the new diesel not-an-M5 is said to start in March, 2012, however, so if it all pans out, we don't have long to wait to find out.