Is it better to use the internal or external air circulation on the highway?
4 Answers
It is better to use the external air circulation on the highway. The external circulation of the car's air conditioning can keep the air inside the car relatively fresh. When driving on the highway for a long time, using the internal circulation for an extended period can make the air inside the car become stale, increasing the concentration of carbon dioxide, which can cause the driver to feel fatigued and tired, seriously affecting driving safety. The external circulation can expel poor-quality air from the car and also be used to refresh the air inside the car. Below are the working principle and method for turning on the external circulation: Working principle of external circulation: The external circulation mode uses a fan to draw air from outside the car into the interior, meaning the air passage between the outside and inside of the car is open. The air blown by the fan comes from outside the car, and even if the fan is not turned on, airflow is still drawn into the car while driving, replenishing fresh air inside the car. Method to turn on external circulation: When the indicator light for the internal/external circulation button is off, it means the external circulation is turned on, replenishing fresh air.
Choosing between recirculation or fresh air mode on highways depends on specific scenarios. My experience is that I usually start with recirculation mode, especially when outside air quality is poor or dusty—it saves fuel since highway speeds make open windows noisy and unsafe. After some time in recirculation, if the cabin feels stuffy, I switch to fresh air mode for a few minutes to refresh, reducing drowsiness. In winter or rain, fresh air mode prevents faster window fogging, improving safety. Avoid staying in one mode too long—excess CO₂ buildup can cause fatigue and slower reactions. I typically alternate every 30 minutes to balance efficiency and comfort.
Choosing the right air recirculation mode on the highway requires careful consideration. I prefer the interior circulation mode as it blocks outside air, reducing the frequency of heating or cooling the air, which lessens the burden on the AC and saves a bit of fuel—practical tests show savings of a few cents. However, prolonged use of interior circulation isn't advisable as it degrades air quality inside the car and can make it stuffy. In situations like highway traffic jams or polluted areas, I switch to interior circulation to avoid exhaust fumes. When the outside air is fresh, I switch to exterior circulation to replenish oxygen, especially during long drives, alternating every 45 minutes to ensure fresh air while still saving money. Don’t forget to regularly clean the AC filter—a dirty filter can impair the effectiveness of both circulation modes and increase vehicle operating costs.
How to choose between recirculation and fresh air mode on highways? My habit is to combine both based on conditions. Use fresh air mode when air quality is good or to prevent fogging, such as after rain or in winter, as it brings in fresh air and keeps the windshield clear for safer driving. In poor weather or when prioritizing fuel efficiency, use recirculation to avoid inhaling dust or pollen. Prolonged use of recirculation can lead to carbon dioxide buildup in the car, causing fatigue, so I recommend switching to fresh air mode for 5 minutes every 30 minutes. Also, remember to check and replace the cabin air filter when dirty to ensure system efficiency. Choosing the right air mode enhances driving comfort and makes the journey more pleasant.
