[Brad Townsend]

I had a water separator installed and now when I drain the water a black substance like oil comes out.
The compressor is dry not oil. I bought a rebuild kit to do a rebuild. Pulled the air water separator apart and it looks like grease inside.
The compressor has 2 air fikters, one for each cylinder. Looked at one and pretty dirty. Was changed in 07. Maybe the dirt is coming through and mixing with the water to make what looks like grease and oil.

Brad

[Fulltiming]

Brad, I suspect what you are seeing is black algal growth in the moisture being removed from the air. You can get that growth in your fuel tanks also. If you haven't rebuilt your engine mounted air compressor recently, you might consider that also. Not sure what else would cause that in a non-oil compressor.