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A gasket is a sealing part fitted between two mating surfaces to stop fluid or gas leaking at the joint.

When the parts are bolted together the gasket compresses to fill small gaps in the surfaces, sealing in oil, coolant, fuel, or combustion gases under pressure and heat.

Gaskets seal joints throughout the engine and its systems — cylinder head, covers, manifolds, and housings. The correct gasket matches the exact joint and is usually renewed whenever the joint is opened.