My understanding was that the Crawfor AOS is maintenance free. The unit separates the oil from the recirculated PVC air and then what it catches eventually returns to the engine via the lower hose back through the PCV valve. Unlike others that have a manual valve that requires dumping from time to time. So you get the oil removed to help keep the backsides of the valves clean yet don’t have to worry about dumping the can.
From their webpage:
Not a Catch Can - Closed Loop and Maintenance Free
An AOS uses centrifugal force to force your engine’s oil through an internal labyrinth system, which makes the oil separate from engine condensation. A catch-can simply collects oil and requires one to either manually empty or pour back in the same, dirty oil. An AOS will automatically drain clean, separated oil back into your engine, without any maintenance required whatsoever. Just install and forget.
From their webpage:
Not a Catch Can - Closed Loop and Maintenance Free
An AOS uses centrifugal force to force your engine’s oil through an internal labyrinth system, which makes the oil separate from engine condensation. A catch-can simply collects oil and requires one to either manually empty or pour back in the same, dirty oil. An AOS will automatically drain clean, separated oil back into your engine, without any maintenance required whatsoever. Just install and forget.
