Oil consumption, but not as expensive as turning on the air conditioner in summer. Air conditioning refrigeration requires the use of a compressor, and the operation of the compressor needs to consume more fuel. In winter, the principle of heating air is different. It does not use a compressor, but uses the temperature of the engine coolant to heat it, that is, the heat released by the engine itself is blown into the carriage by a blower. Although the operation of the blower needs electricity, it will increase the engine load and thus consume oil, but it is far less than the oil consumption when the air conditioner is turned on in summer.
But don't turn on the warm air when the car is just started or still warm, because the engine is not hot, and the cold air blows in, which is also a waste of electricity and increases the engine load. It is best not to turn on the warm air when parking at idle speed.
If you want to save fuel and dissipate heat, it is suggested that the owner can start the external circulation after driving 40-50 yards, and the fresh air flowing outside the car will also pass through the warm air tank, bringing heat.