C5 II 2.0 hdi oil level lowering to mid point

[aneesh84]

I have a C5 2005 2.0 hdi 136. Owned this car since 2016.

Ever since I owned this car I noticed a pecularity that everytime I would top up the engine oil to the max level, after one drive it would quickly drop down to midpoint of the dipstick and stay around there. I assume the excess would be blown out from the oil breather. I didnt notice any leaks anywhere. The last time oil was changed last year the dip stick level was kept at midpoint, and now after being driven 3000 miles the oil level is 3 mm below the last oil fill position (half way mark).

Still purplexed why any oil above the dipstick midpoint reduces on the first drive and then its fine?
Any suggestions/advise?