Hapco Pro-Seal concentrated formula is guaranteed to stop existing leaks in any fluid system: Engines, transmissions, differentials, power steering, rack and pinion, rear axles, gear cases, reduction gears, trim tabs, pillow blocks, transfer cases, heavy equipment and any hydraulic system (jacks / cylinders / pumps). This easy-to-use treatment quickly restores the flexibility, elasticity and tensile strength of all rubber seals to stop current leaks. It does not contain petroleum distillates, which can harm or destroy seals, and is 100% non-clogging. Pro-Seal can also be added at any time as a seal conditioner to help prevent future leaks. Compatible with all conventional and synthetic oils / fluids. Directions: With engine or equipment off, add one bottle of Pro-Seal to fluid reservoir where leak is occurring (or 1 OZ. per quart capacity). Do not use in brake system. Drive vehicle or operate machinery as normal to allow circulation of fluids. Most leaks are stopped within a total of 2-5 hours of fluid circulation. After the leak is repaired, Pro-Seal can safely remain in the system until mileage indicates need for oil / fluid change.