- The oil level sensor is installed at the bottom of the oil pan.
At this odometer reading, you may want to replace it using Genuine BMW sensor. I'd do this at the next oil change.

- Re oil consumption, search the web for "BavarianE39 CCV Mod".
I posted my own details in that long thread.

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1998 E39 528i 5sp MT
2006 E53 X5 3.0 6sp MT