Do a search on blowby and you will find a number of discussions on this topic. At one time I suggested a scientific comparison utilizing garbage bags placed over the oil fill hole, timed to see how long they fill.
It is nothing to worry about as long as the engine starts and runs well.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13