BlueDevil Hydraulic Stop Leak permanently fixes hydraulic leaks for good. The hydraulic leak sealer is a simple way to extend the life of your machinery by patching leaks before they become costly problems. Simply add it to your hydraulic system to seal minor leaks in hydraulic lines, fittings, o-rings and seals. Once added, the treatment begins working immediately and continues sealing new leaks as they form for the life of the fluid change. Keeping hydraulic systems running smoothly can be a hassle, but with this reliable sealant, you can say goodbye to leaks for good.