Wynn's Engine Stop Leak is a special blend of chemicals formulated to stop engine oil leaks & drips that can result from the drying out & shrinking of engine neoprene, rubber seals & O-rings. Prevents & stops engine oil leaks without demounting. Restores the elasticity of rubber & neoprene oil seal rings & O-rings. Lubricates & maintains engine seals in good condition. Will have no effect on the viscosity or performance of engine oil. Is compatible with all mineral & synthetic, single- & multigrade oils. Does not harm catalytic converters. Recommended for all petrol, LPG & diesel engines of vehicles & stationary equipment. Works on all rubber & neoprene seal rings in the engine. Effective for excessive leakages at the rubber or neoprene valve stem seals.