Sewers Aid was thought to be a miracle for uncooperative threads when it first came on the market. However, repair techs soon found that is was leaving alot of 'goo' for lack of a better word.. on the insides of the machines. We were soon told if we absolutely had to use it, only use a tiny tiny drop on the needle, no more using it on the spools themselves. Just some information I am passing along. I worked @ a dealership so was current on thoughts by the tech repair dept.