Gasket Sealant

What Is Gasket Sealant and Why Does It Matter?

Every time two engine surfaces meet — oil pan to block, valve cover to head, timing cover to front cover — a reliable seal is the only thing standing between a clean engine bay and a slow, costly leak. Gasket sealants are chemical compounds applied to mating surfaces to fill microscopic imperfections in machined metal, supplement or replace cut gaskets, and maintain a fluid-tight barrier through the heat cycling, vibration, and chemical exposure that engines generate every day.

Choosing the right sealant is about more than convenience. Modern engines use aluminum, bi-metal alloys, and high-tech plastics that expand and contract at different rates. A sealant that bonds too rigidly can crack under thermal stress; one that stays too soft may wash out under oil pressure. Understanding the differences between sealant types — RTV silicone, anaerobic, non-setting, and cut-gasket coatings — helps ensure a repair that lasts.

Types of Gasket Sealant

• RTV Silicone (Room Temperature Vulcanizing): Cures when exposed to moisture in the air, forming a flexible, rubber-like seal. Ideal for oil pans, valve covers, and timing covers. Can be used with or without a cut gasket.
• Non-Setting / Non-Hardening Compounds: Remain permanently pliable, allowing easy disassembly and reuse. Excellent for applications requiring frequent service access or copper head gaskets.
• Anaerobic Sealants: Cure only in the absence of air and in the presence of metal ions, making them ideal for close-tolerance metal-to-metal flange joints.
• Cut Gasket Coatings: Applied over paper, cork, or composite gaskets to enhance their sealing capability against automotive fluids and gases.

Key Considerations When Shopping

Before selecting a gasket sealant, consider the operating temperature range of the application, the types of fluids the seal will contact (oil, coolant, fuel), whether the joint needs to be disassembled for regular service, and whether the application is OEM-specified. Always confirm that your chosen product is sensor-safe if it will be used near oxygen sensors or emissions components.

Top Gasket Sealant Brands

Permatex is the dominant name in gasket sealants for good reason. Permatex's roots in the category date back to 1909, when founder Constant Benoit's experimental gasket cement kept a race car running through a grueling 24-hour endurance event. Today, their lineup — including the iconic Form-A-Gasket and a wide range of RTV silicone gasket makers — offers solutions for virtually every sealing scenario, with formulations featuring outstanding oil resistance, sensor-safe chemistry, and compatibility with modern aluminum and bi-metal engine components.

Aisin Automotive Casting Tennessee brings OEM-level engineering to the gasket sealant category. As a Tier-1 supplier with deep roots in Toyota's manufacturing ecosystem, Aisin's sealant products are formulated to meet exacting factory specifications, making them a trusted choice for technicians working on Japanese import vehicles where OEM-spec materials are critical.

Hylomar is the specialist's choice for non-setting gasket compounds. Originally developed in collaboration with Rolls-Royce, Hylomar Universal Blue has earned a reputation among professional builders and Formula 1 teams for its permanently flexible, non-hardening formula that resists oils, fuels, coolant, and combustion products while allowing unlimited assembly time and easy disassembly for service.

ThreeBond brings over 60 years of precision sealant technology to the automotive market. Their OEM-approved liquid gaskets are widely specified by Japanese motorcycle and powertrain manufacturers, and their RTV silicone products — known for exceptional vibration absorption and heat resistance — are favored by engine builders working on everything from economy cars to high-performance motorsport applications.

Diode Dynamics rounds out the category with a focused sealant offering suited to automotive electrical and lighting installations, where a reliable moisture barrier is just as important as in the engine bay.