Under normal circumstances, automobile air conditioning accounts for about 20% of the engine power, that is, the fuel consumption of a car with a fuel consumption of 10 liter per 100 kilometers will increase by about 2 liters in summer when the air conditioner is turned on. The specific value can be converted according to the fuel consumption of the vehicle engine. The following are the precautions for using car air conditioners: 1, the temperature difference is too large and it is easy to catch a cold: the suitable temperature of the human body inside the car is 5 degrees lower than the outside, for example, the temperature outside the car is 35 degrees, and the air conditioner is best set at about 30 degrees. Even if the air conditioner is set to 18 degrees or 20 degrees, the real cooling capacity is difficult to achieve. On the contrary, a large temperature difference will stimulate the driver and passenger to get cold and fever. 2. Both internal and external circulation should be used: Some car owners use the internal circulation mode for a long time in order to improve the cooling or heating effect of air conditioners. In this mode, the air between the car and the outside of the car can't circulate naturally. The car is just like a closed independent space, which can improve the air conditioning efficiency to the maximum extent, but it is not suitable for long-term use and external circulation switching, otherwise it will easily cause dizziness or chest tightness for drivers and passengers, which will lead to danger.