Quote: Crops can become slow for many reasons if only because the good bacteria is gone from the crop itself. A slow or sour crop, many times is just a yeast infection. Oil will make the yeast infection worse. Oil is hard on the liver. So I cannot think of one good reason to give a bird oil.
If in fact this slow crop is caused by a blockage in the gizzard from grass or hard vegetation, oil will harden this blockage and block it up even more. Turns it gummy.
So I am sticking to my guns here, there is no good reason to ever give a bird oil.