So, back in the 70's, I worked in a factory that built home window and automotive air conditioners. One of the significant things I learned was that the refrigerant used was mixed with oil to provide lubrication to the compressor/pump.

So, my question: If 'all' the 'freon' leaked out, and you get the leak fixed and then recharge it with Freon - does the Freon have lubrication oil in it? Or do modern systems not need oil in there?

Iv often wondered about this. See, it seems that "recharged" systems often fail in time. I've always wondered if a step is not being missed here. Does anyone know?