Is it okay to keep the external air circulation on while driving on the highway?

[SanLilliana]

It is not advisable to keep the external air circulation on while driving on the highway. Here are the specific details: Introduction: When the external air circulation is turned on, outside air enters the vehicle, keeping the interior fresh and ensuring smooth breathing for passengers. However, because outside air is continuously entering the cabin, the air conditioning compressor needs to work constantly to maintain the temperature, which consumes more fuel. Correct use of external air circulation: When driving on the highway with smooth traffic and good road conditions, you can keep the internal air circulation on for extended periods to maintain the temperature. However, it is essential to switch to external air circulation for 5 to 10 minutes within an hour to allow fresh air in and increase the oxygen level inside the vehicle. Learn to use both internal and external air circulation flexibly. For example, in situations like tunnels where the air quality is poor, you can switch to internal air circulation to effectively prevent dirty outside air from entering the cabin. Conclusion: Using either internal or external air circulation for extended periods is incorrect. The right approach is to alternate between them flexibly based on the actual situation.

[McSophia]

It's perfectly fine to keep the external air circulation on while driving on the highway, especially during long trips. The fast-moving air outside continuously refreshes the cabin air, preventing carbon dioxide buildup that can cause drowsiness. Last month, I drove from Beijing to Qingdao with the external circulation on for four hours straight—no fogging on the windows, and the air stayed fresh. However, pay attention to the weather; switch to internal circulation in smoggy conditions or when passing areas with heavy truck exhaust. Prolonged use of external circulation may increase the AC load and slightly raise fuel consumption, but safety comes first, right? Remember to open the windows occasionally for even better ventilation.

[SanKeira]

I've been doing cross-province freight transport for years, and using the external air circulation on highways has become a habit. The biggest advantage of external circulation is preventing driver fatigue, as the continuous supply of fresh air helps keep the mind clear. Especially in summer, even with the AC set at a higher temperature, it feels cooler with external circulation compared to the stuffiness of internal circulation. However, there are two things to note: first, if there's a lot of pollen or dust outside, it can easily cause sneezing; second, on rainy days, it's necessary to use the defogging function, otherwise, the windshield can fog up easily. Actually, you don't need to use external circulation the entire time—opening the windows for a few minutes when passing through mountainous areas or less crowded roads can be just as effective.

[SabrinaLee]

Using the external air circulation at high speeds is good, but it's not necessary to keep it on all the time. With severe PM2.5 pollution in cities nowadays, the external air circulation directly draws in polluted air from outside, which isn't ideal. My experience is: use external air circulation on sunny days with light traffic, and switch to internal circulation in heavy traffic or tunnels; using the automatic temperature control feature of the air conditioning is more convenient than manual adjustment. The most practical feature is the automatic switching between internal and external air circulation, which maintains airflow while filtering pollutants. Remember to ventilate for five minutes during rest stops every two hours—it's healthier and more fuel-efficient than using external air circulation the entire time.

[Marc]

It depends on the traffic conditions. Using the external air circulation in the city just means inhaling exhaust fumes, but it's quite suitable on the highway. Keeping the external air circulation on ensures air flow, but remember to change the cabin air filter frequently, especially during the willow catkin season in the north. Last year, when I was stuck in traffic on the Beijing-Hong Kong-Macao Expressway with the external circulation on, the filter got clogged in less than half an hour, and the airflow from the vents noticeably decreased. Also, for cars with automatic air conditioning, don’t set the temperature too low—around 22°C is the most comfortable. Setting it too low forces the compressor to work continuously, which consumes more fuel. Actually, the key to good air quality inside the car is the filter—using a high-quality activated carbon filter is more important than the circulation mode.

[SanJayla]

Using the external air circulation is certainly fine, but it's recommended to combine it with other operations. Every time I drive on the highway, I first use the external air circulation for 5 minutes to ventilate, then switch to auto mode. This saves fuel and protects the AC system, as the external air circulation can mix in hot air from the engine compartment, increasing the compressor's load. Two key points to note: first, don't smoke when using external air circulation, as the airflow can blow ash all over the car; second, switch to internal air circulation before toll booths to avoid inhaling exhaust fumes from the vehicle ahead. Another clever trick is to slightly open the sunroof while using external air circulation, which doubles the ventilation efficiency without being noisy.