Which component affects engine cooling efficiency by regulating coolant flow?

The thermostat plays a crucial role in regulating engine cooling efficiency by controlling the flow of coolant within the engine system. As the engine heats up, the thermostat monitors the temperature and opens or closes to either allow or restrict the flow of coolant to the radiator. This helps maintain the engine at its optimal operating temperature, ensuring it does not overheat or run too cold, which can affect performance and efficiency. By doing so, the thermostat ensures that the engine's thermal management system operates effectively, contributing to overall cooling efficiency.

While the water pump is responsible for circulating the coolant throughout the engine and the radiator, it does not have the capability to regulate coolant flow based on temperature. The radiator's primary function is to dissipate heat from the coolant, and the oil cooler helps in maintaining the temperature of the engine oil but is not directly involved in managing coolant flow. Thus, the thermostat's function of regulating coolant flow makes it the correct choice in this context.