ACDelco Dielectric Silicone Grease is a silica thickened dimethyl silicone fluid. It has a broad temperature range from -65 degrees Fahrenheit to 400 degrees Fahrenheit (-54 degrees Celsius to 204 degrees Celsius). This product is non-corrosive, oxidation resistant, electrically insulating, radiation resistant, chemical resistant, and water repellent. ACDelco Dielectric Silicone Grease is designed to coat the inside of spark plug boots to prevent them from sticking to ceramic insulators. It also checks corrosion by improving boot seal. Do not apply to silicone rubber components, as the grease will react with and harm that material.