If all the cyls are wet with
oil evenly I would doubt it is porosity, an intake gasket or the like. My guess is the crankcase venting system is not working properly or is insuffecient. Does he have valve cover breathers or intake manifold breathers? Both? Neither? I know a guy who installed a rebuilt engine with new aftermarket valve covers that he didn't open the breather holes on. The engine would barely turn over. Is the PCV (if installed)
stuck open? Engine vacuum can easily suck up a quart of
oil every 50 miles.
HTH,
Mike