The reason for checking oil hot is the expansion you mentioned and that the sump has enough reserve to keep feeding the oiling system without interruption after the oil pump has fully purged the oil galleries.

When I do a cold check I get a slightly high level - abt 3/4 of the dipstick, but when I do a hot check I get 1/2 dipstick which is perfect, I have always maintained all my cars at such engine oil level, unless it was recommended by the manufacturer to a special mark on the stick.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)