Blow by is increased whenever you allow the compression to escape the combustion chamber during the power stroke. The two most likely locations are past the rings (worn or broken) and past the not fully seated valves (bad seats/out of adjustment). Both of these conditions show up as low compression numbers when doing a compression test.

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1976 240D
1987 560SL
2007 E320 Bluetec
1998 C280 (now son’s car)
1982 240D Manual - Sold