I took one of my sewing machines, not a featherweight, to my OSMG. The case reeked of old sewing machine oil. He reached for a small spritzer bottle and gave it a couple of spritzes. I asked him what is was and he said patchtouli oil. I don't smell old oil anymore just patchtouli. I am guessing that the patchtouli oil is overpowering the old oil. I have not tried it on the featherweight cases though.