At what engine coolant temperature can the car's heater be turned on?

[OFrancisco]

The car's heater can be turned on when the engine coolant temperature reaches 80°C to 90°C. The normal operating temperature of a car engine is generally between 80°C and 90°C, while some high-performance engines may operate at temperatures above 100°C. Since the heater's warmth comes from the engine coolant, turning on the heater too early will slow down the coolant's warming process and prolong the warm-up time. After a cold start, the temperature gauge typically begins to show readings around 60°C, and you may feel warm air from the vents. However, for engine protection, it is recommended to wait until the coolant temperature reaches 80°C to 90°C before turning on the heater. Before the engine reaches its operating temperature, the fuel-air mixture's poor atomization may increase fuel injection, leading to carbon deposits. Additionally, when the heater is turned on, the coolant from the heater core will flow back into the engine block, further extending the engine's warm-up time.