I just emptied the oil out of my new one and filled with the recommended ounces of new oil. I got the compressor from rock auto. If your system was open for any time, or your comp.failed and got sh*t in system then you need to flush out system, rock auto sells a good flush canister with the right fitting to hook up an air compressor to. I use and recommend ES12A it's a freon alternative, it has many benifits. I've researched it plenty , you 'll love this stuff.
Not sure. I only ask because there was a sticker on the cover plate where the adapter for the hose connection attaches that said it was filled with shipping oil and not refrigerant oil. I'll take another look. Perhaps I just didn't read the sticker well enough.