I use an Oceanus, it is a much better unit than the JRII as it has a larger sump and an oil pump, which the JRII doesn't have, plus higher output capacity. I have pumped Nitrox 40% through it for years without issue. The standard filter on the unit is a P21. Replacement cartridges are less than $50. That is a great deal for a very well built compressor. I pulled mine right down after 1000 hours to check it all out and it was like brand new inside. I'd say buy it.
Just run synthetic oil and you will need to pull the heads, intercooling coils, filter, separator and valves out to clean them prior to using synthetic lube. This sounds like a big job, but it is not really, compressors are very simple. While you are at it, I'd recommend replacing the second stage valve o-rings for peace of mind. Service manuals are easy to find on the internet.