I have a mapped 330d running on 0w30 and it looses no noticeable of oil between 7k services. It isn't thrashed, but it does get some good long runs.
If there's no signs from the turbo, my next port of call would be the PCV system - more specifically this part:
https://vanos-bmw.com/product/repair...81-11128507607
If that spring or diaphragm malfunctions, it creates excessive suction on the PCV system, meaning the intake manifold is sucking in 'wet' oily crankcase air without the cyclonic separator having done its job.
I had a similar problem with my old m54 engined Z4. It suddenly started consuming huge amounts of oil and it was the PCV.