Wow! Awesome report on M1 0w40...you should read the Porsche boards and see how many of them freak out if they go over 5000 miles on this oil...Some of them change it at 2-3000 miles and it is a 9 quart sump.
With TBN of 4.4 after 7400 miles, the OCI can be extended to 10-12k miles. The recommended OCI is up to 20k miles since model year 2005, I think M1 0W40 is toasted at 15k miles according to this UOA. Why Porsche is recommending such long OCI ? Which oil can lasted that long in such a high performance engine ?
I think Porsche lowered it to 12k/1yr now. These vehicles hold a lot of oil. 9-10qts is a lot of oil so longer drain intervals are doable.
15k seems to be about the max you can go with most synthetics. SSO, S3k & D1 are good for a lot more with large sumps in diesels but the others seem to loose it around the 15k mile mark unless all other variables are practically perfect. Still, oil is relatively cheap and getting 10k out of any oil is good considering most people drive 12k/yr.