[ademonrower]

I don't know in quantitative terms yet, because I've only driven around 200 km (120 miles) so far, but I can see a little oil starting to collect. The qualitative test - and I have (my wife tells me) a very good sense of smell :-) - is that I can hardly smell the exhaust anymore. I have tuned my carburettor very finely, so hardly any gasoline smell: it was basically just a little oil getting burned. I suspect that in older cars (mine is from 1979) the combination of slightly more piston blow-by and less efficient PCV in general produces more crankcase gas. That said, the Volvo redblock engines - cast iron block - wear very well (it's not rare to see the diamond honing on the cylinder walls still almost factory-perfect after 500,000 km!). My bottom line is that my particular modification worked well for my particular car. That might be luck, and at the most it's an experiment with n=1 :-)
Thank you also for alerting me to a potential caveat: particularly in winter, you don't want simply to tip the collected liquid back into the engine: it might well contain lots of water and even be an emulsion... hmmm... in general I think it's probably a good idea to check the liquid anyway... and probably just tip it into a used oil container... probably does more harm than good to recycle it... ?