This may be a silly question. But wouldn't it be possible just to put some kind of inline filter in the hose? Like a frogskinz material that would let the air through no problem but would slow down the oil. I really want to protect everything... but $200 seems steep. There has to be a cheaper solution
The reason filters are not used, is that in order to stop or slow down the oil the filtering material would have to be so fine, that it may not allow for proper crankcase breather air flow. Also once oil/moisture has been exposed to the filtering material, the filter can become restricted, or even freeze closed as mentioned above by Snowmow.
Because any pressure build up within the oil tank can have a negative effect on dry sump oil pump scavenge flow rate. It is critical that the internal pressure within the oil tank be as close to 0 psi as possible anytime the engine is running. Crankcase breather air flow must be able to flow freely without a restriction, which is why the breather hoses are normally 5/8” to ¾” in diameter depending on the application.
Oil tank venting air flow increases dramatically as RPM/engine load increases, manufacturers typically will opt to tie the breather vent into the engine air intake after the engine air filter. This eliminates the possibility of a restriction in the breather vent system, due to a plugged breather filter, while at the same time insures that the air exposed to the oil tank is clean and filtered.
