I have an ammonia plant, with 5 screws and 2 pistons. I have 4 recievertanks, one priority tank, 5 freezingtunnels, and one big freezingroom. I now and then fill oil on compressors. And now and then I take the oil out of the plant. But I fill more oil then I take off. Where can it be? I take oil from under the prioritytank, and I have an oilboiler also. But still I fill up more then I take off. Suggestions?