Keeps hydraulic seals soft and pliable. Reduces friction and wear in hydraulic systems. Cleans and prevents harmful formation of sludge and varnish. Helps hydraulic systems run cooler and last longer. Mixes with all factory-approved hydraulic fluids and synthetics. Rislone Hydraulic Stop Leak is compatible with all petroleum based, mineral oil, and synthetic fluids. Do not use with water-glycol or phosphate ester flame retardant hydraulic fluids. Do not use in brake fluid systems. After time, hydraulic seals and O-rings tend to dry out and shrink. Rislone revitalizes these seals and O-rings and makes them soft and pliable again.