Does refridgerant always contain oil for the compressor? At Wal-Mart I had tons of choices, but none that I felt comfortable buying. They all either contained stop-leak chemicals or made no mention of oil for the compressor. They had cans of oil too, but there were different kinds and I would prefer to just buy one can of refridgerant/oil. I have heard bad things about stop-leak additives, so I didn't want to buy something with it. Does anyone know of a brand that contains just refridgerant and oil and where I can buy it?