How does B8 ride compared to Sach M-sport? Is it more firm? My priority is skewed more to comfort rather than handling for the car. I've change the diff oil last year together with the GB's oil. Bought the original BMW diff oil from Bavarian Auto. You'll need 1L (1 bottle) for the job.The workshop will use a suction pump to remove the old oil and pump the new oil into the differential until its full. After the change, the car felt smoother overall.