I'm not following. If the breather tube was not attached, how would any oil be getting into the air filter housing? As far as I know, the breather tube is the only possible source of oil there.

There's one other thing that puzzles me: How was the breather tube clogged? If it was disconnected it would normally just vent into the air. This by itself could be the source for some oil, depending on how much blowby you have.

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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