@justalubetech Thanks for your thoughts. My compressor came with only shipping oil in it, so I have to drain it. And since I have a leak in the high pressure line, which I'm replacing, I need to compensate for that. Plus whatever was in the drier, which I'm replacing. They also warn you in the instructions never to put more than half of the system spec in the compressor or in my case not more than 3oz, because too much oil in the compressor, before it has circulated through the system, can cause it to lock up when it is run for the first time. So at least in my case, in seems a little more complicated. It also seems like if I don't add extra oil somewhere else in the system, in my case I'm going to use the discharge hose, I would risk having less than spec in my system and, as others have said, too little oil is worse than too much (at least if you only go over by an oz or two).