Disappearing Oil (no leaks!)

[Dreamsound@xxxxxxx]

I tried asking this question earlier and got no responses, here's a different 
approach:

      Why would oil get into the vacuum hoses and the throttle body?  I've 
been told there is a check valve to keep it out of the vacuum system, 
sometimes called a PCV valve (positive crankcase ventilation valve?) or 
something similar.

1)  Is oil supposed to be in the vacuum hoses?  (my mechanic says "no")
2)  What keeps it out?  Where is it?

The car is a 1991 E30 318is, M42 motor, consuming 1/4 quart of oil per 
fillup.  There are no leaks to be found.  In the last few thousand miles this 
has been getting worse and worse, the rebuild was supposed to fix the problem 
and refresh the engine but the oil consumption is still present.  Please let 
me know if there is another list I could post this to, such as one for 318's 
only, etc...
Thanks,

Mike Crotty
1991 318is

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