Interesting and worth a try if this is a problem with your M3W. I have been using Motul 7100 4T 20w-50 V-Twin fully synthetic oil since after the first two oil changes, now almost 30,000 miles. The oil tank draining its contents into the sump has never been an issue on my car. I think the oil drains down through the pump and possibly variations in clearances would explain why some cars are more prone to this problem than others? The change to a mineral oil would be an easy check though, hope it works for those with this issue.
Last edited by planenut; 20/03/21 09:09 AM.
