The news comes courtesy of unnamed sources that say the first diesel from the M division will supposedly pack a tri-turbo, six-cylinder diesel nestled beneath a modified hood. Two versions are rumored to be available: a traditional RWD variant badged the M550D and an all-wheel-drive version that appends the xDrive moniker to the end. BMWBlog's people on the inside say that the RWD model will hit 60 mph in 4.9 seconds, with the AWD doing the deed in 4.7 ticks.
The good news: The M-fettled diesel X6 will reportedly go on sale in March of 2012. The bad news: It's a Euro-only affair.