Actually you're not the first one who has blowby but apparently good compression. From what I've read leaking valve seals can cause blowby too, but wouldn't that reduce compression as well? One day I may do a valve job on my 240D to see if I can reduce the blowby and oil consumption, but my oil consumption is not very bad at this point, I think it's about a quart per 2000 miles.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL