Thermostat gaskets are designed to provide a seal between the thermostat housing and vehicle engine. The thermostat gasket must be compatible with the vehicle cooling system; the Tridon thermostat gasket range has been carefully researched and engineered to suit each specific application. Most new thermostats come with their own gaskets or rubber seal, but not all. Some thermostats come with a rubber seal instead of a traditional gasket. Before installing, apply a light coat of fresh coolant to the seal. Some models use a liquid gasket instead.