I drove the M4 through an entire winter including a few weeks of Canadian snow storms on Conti DWS 06 (all season) tires. No issues except getting stuck in a parking spot in 1 foot of snow. No regrets at all - i will do it again to enjoy the car all year. The car is well balanced, i enjoyed alot on empty roads
As a bonus, when trading in its worth the same as a summer only driven car
