BMW Canada's fuel economy ratings
According to the BMW.ca website the fuel economy for the M3 is as set out below.
City, man/auto (L/100km) 15.3/15.3
Combined, man/auto (L/100km) 12.8/12.9
Highway, man/auto (L/100km) 9.7/9.9
This says that the 6MT gets slightly better fuel economy than the 7-speed M-DCT equipped car. However, the BMW international website says that the M-DCT gets better fuel economy than the 6MT. The press release for the new transmission in January also said that M-DCT "reduces fuel consumption by a significant margin".
What gives? I have a question submitted to BMW right now on the matter.