Lucas Engine Oil Stop Leak is a unique formulation of Lucas additives and base stocks designed to stop leaks in engines. It is also an exceptional additive for worn and older engines, reducing engine noise and oil consumption while raising oil pressure. It contains no harmful solvents and can actually extend engine oil life by 50% or more. Leaking engines are usually older engines. Lucas Engine Oil Stop Leak is not only a leak stopper but also an excellent additive for worn engines. The user can expect less engine noise, higher oil pressure and less oil consumption as the Lucas additives fill the space between the worn parts. Lucas Engine Oil Stop Leak is also effective at stopping leaks in automatic transmissions, hydrostat transmissions or hydraulic systems. 10% is usually adequate - more can be used in badly worn units. In gasoline engines, a puff of white smoke out the tail pipe in the morning is a sure sign of worn valve seals allowing oil to seep past the valves into the combustion chamber when the engine is not running. This is a sign of a high mileage engine. Allow a few days for Lucas Engine Oil Stop Leak to correct this problem. To keep this problem corrected a quart (or litre) will probably have to be added with each oil change. Use 20% of system capacity (example: 1 quart of Lucas Engine Oil Stop Leak to 4 quarts of motor oil.)