Is the engine thermostat part of emission system?

Yes, the engine thermostat is part of the emission system. Its main function is to control the flow of coolant through the engine and maintain an optimal operating temperature. When the engine is cold, the thermostat restricts coolant flow to allow it to warm up more quickly. As the engine reaches its desired operating temperature, the thermostat opens up and allows coolant to circulate more freely, preventing it from overheating. This precise temperature regulation also contributes to the overall reduction of harmful emissions as the engine operates at its most efficient temperature. By ensuring the engine runs at the optimal temperature, the thermostat indirectly contributes to reducing emissions and meeting emission standards.