What exact oil did you use? Would you mind checking? There's so many varaiations even with the correct spec, its hard to wrap my head around it.The conclusion I took from there was that Fuchs is one of the best value fully synthetic trusted ones with Millers if you want o spend some extra money. Has been my go to ever since for all my cars and those of friends (obviosuly with the correct compliance - C3 and LL04, etc). I was using Fuchs on the 330D when it wasn't using a drop in between changes.
The last 2 changes, I have used this - Millers Oils Trident Professional C3 5w-30 Fully Synthetic , this is also when the oil consumption started. I don't want to jump into conclusions, but... Before I used Shell Helix Ultra ECT C3 5w-30.