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Almost certainly, any filter on the market that claims to be maintenance-free is allowing sub-to-low micron-sized oil droplets to get by. Some have no filter media at all; they rely on coalescence from impaction and surface temperature variation. The ironic thing is that while this merhod of trapping oil is effective for trapping some of the airborne liquids, having the catch can mounted close to the engine defeats the "purpose", so to speak.
- Keep the "trap" low and away from any heat source (like the engine).
- Use filter media that is dense enough to trap a large percentage of oil and water, yet will not clog within a few hundred miles of driving.
- Replace the filter when vacuum pressure drops by 2-3 inches of mercury when compared to free-flowing vacuum pressure.
If your filter never needs replacing or if you have no filter, chances are high that oil is getting through. Donaldson makes excellent oil/particulate separator filters for large trucks and busses and they specify a maximum number of running hours before the filter needs replacing.
Lastly, industrial air/oil separators always position the filter element at the very end of the enclosure path. All captured oil is either drained away or kept on the upstream side of the filter. Many catch cans allow blowby gasses to be exposed to captured, sloshing oil, just before it exits an unfiltered opening. This is certainly less than ideal.
After reading and getting all the information I can get my hands on I have decided either the Saikou Michi or the RevExtreme catch can. Saikou makes a duel can that looks to be the best you can get for an LS engine.
I have the Elite and it werks! I had quite a bit of oil in the intake and the last time I had it apart, I found none! I like the way they have the mounting.