Repairing old ECOA stacker, don’t know model no., can post pic of one if needed. Had to lay it down horizontal to get at the wheels, and about a gal. Of black fluid drained out. That’s obviously the “hydraulic fluid” but is thicker than most hyd. Fluid. Is black and smells more like motor oil. Need to replace the loss, so what to use? Think this machine dates from 1970’s, long before Presto Took them over. I called Presto in AR but they had no knowledge of older models.