Genuine OEM Audi Engine Thermostat, part number 059121111AA. This essential component plays a crucial role in the engine cooling system by regulating the engine's operating temperature, ensuring it reaches and maintains optimal thermal efficiency. Constructed with durable materials, it features a precise spring-loaded valve mechanism. Using a genuine OEM thermostat guarantees accurate temperature control and reliable operation, preventing both overheating and undercooling that can lead to engine damage or reduced fuel economy.