I had that same kind of scuzzy thing happen to me years ago when I got suckered into trying a lubricant additive. It was introduced into the hydraulic system of a track loader. It had claims of of all this anti-wear and cooling advantages over just using the recommended hydraulic oil. At one point the loader sat over the winter and when I opened up the hydraulic tank in the spring, the walls were coated in this black sludge. That was money well wasted.
Brian
