What outcome results from a malfunctioning thermostat?

A malfunctioning thermostat can lead to fluctuating engine temperatures because the thermostat is responsible for regulating the flow of coolant between the engine and radiator. When it operates correctly, it maintains a consistent engine temperature by opening and closing at predetermined thresholds. If the thermostat sticks open, the engine may not reach its optimum operating temperature, leading to cooler temperatures, while if it sticks closed, it can cause the engine to overheat. Both scenarios result in an inconsistency in temperature, hence the outcome of fluctuating engine temperature. This affects engine performance and efficiency, which can ultimately lead to additional engine complications if not addressed.