I just got my hands cleaned from the oil today. A good operator can rub the oil between his fingers and smell it and tell you if it will sell or not because BS&W.( Basic Sediment & Water) Most contracts with the pipeline companies has a limit of 1% BS&W. If oil has water in it, even 1.5% it will change the way it smells and feels. If you open a 1/4 valve and spray the oil into a bucket and your oil is clean, you will see lots of light brown bubbles. When the water is present the bubbles will not be there. I know I am rambling, but this is what myself and my crew just finished doing. Our treater watered out and we had to re-clean some of our oil.