I have a little jun-air 6-15 air compressor, like the one in the photo. Its is basically a sealed refrigerant type, and is the quietest compressor I've ever heard, not much louder than a household refrigerator. I have it teed into my main air line with a 7.5hp IR so the big one only comes on for high demand. The air lines and tanks have enough capacity so the big one rarely turns on. I need to add a bit of oil to the jun-air, cap says sj27 oil. Of course this oil is like $75 a pint and probably garden variety oil of what type I don't know, other than loads of people repackaging what the stuff really is in containers with jun-air sj27 "replacement" labels. Anybody know what it really is?
