I thought you might say that... The problem is that I have no history so no idea when last oil was added. Besides which, the car was pressure washed before I bought it so no residue.

If someone added an ounce too much, would that ruin the system. I'm thinking adding a small amount might be in order, like maybe an ounce. I know this not how you operate in general; I'd just hate to see my compressor lock up for lack of maintenance. It's obviously throwing oil. A full flush is not called for since the system works, and besides, we hardly use ac here anyway!

Or will the compressor warn me when it's low on oil by squeaking before it locks up?