That's been around forever It seems.. I posted it up here awhile ago.. The bottom line is you/we need much better oil than we think.. The top shelf good stuff is inferior to the bottom shelf race type oils
We had a huge convo on here a few months back check it out
This document shouldn't be taken out of context. On the particular motor they based this off of, thicker oil was not detrimental to oil FLOW. Seems like clearances are tight on N5x, so, you'd have to do the same kind of testing to show using thicker oil is NOT detrimental to flow as well. There were M motors that suffered spun rod bearings because the oil BMW recommended (10w60) was too thick for daily driving and should've only been used on a road-course where oil sees 280f temps. You can't magically increase clearances to put a larger wedge of oil between moving parts. If oil is thinning out from performance driving, you'll see pressure start to drop, and an adequate oil wedge may fail to form as a result. This document is 100% based off anecdotal experience. Nothing scientific about it.
Also, I've seen that ZDDP content is not good for daily drivers that see frequent cold starts. ZDDP content protects surfaces once the additive is AT TEMPERATURE in the event that surfaces are wiped of oil. Otherwise, it been shown that higher ZDDP content increases wear on startup.