Should You Use External or Internal Air Circulation on the Highway?

[Trevor]

It is recommended to use external air circulation on the highway and switch to internal circulation when the outside air quality is poor. Below are the reasons for using external circulation: Enhance Driving Safety: When driving at high speeds, using external circulation and occasionally switching to internal circulation helps maintain air circulation inside the vehicle, keeping the air fresh. This prevents excessive carbon dioxide buildup, reducing drowsiness and fatigue, thereby improving driving safety. Improve Driving Comfort: Highways are generally far from urban areas, and the air quality is usually good. External circulation continuously supplies fresh air to the cabin, ensuring good air quality and enhancing driving comfort.

[DiPresley]

Every time I drive on the highway, this issue comes up. Generally speaking, using the external air circulation is safer because it continuously draws in fresh air, preventing carbon dioxide buildup inside the car and keeping you alert and awake. However, on the highway, if the outside air quality is poor—such as during smoggy weather or when passing through industrial areas—I immediately switch to internal air circulation to block dust or unpleasant odors. The advantage of internal circulation is that the air conditioning cools or heats up faster, saving some fuel, which is quite practical during long-distance driving, especially in summer when the AC is on. However, prolonged use of internal circulation can make the air stuffy, so I make it a habit to switch to external circulation every half hour to get some fresh air. Don’t forget to check the cabin air filter—if it’s dirty, it will affect performance, so don’t slack off on the highway. In short, being flexible and adjusting accordingly is the smartest approach—don’t stubbornly stick to one mode.

[DiPresley]

I'm quite concerned about fuel efficiency, especially when driving on highways. The external air circulation mode draws in fresh air from outside, requiring the air conditioning to work harder to regulate the temperature, which consumes more fuel, particularly when cooling. The internal circulation mode is more economical as it only recirculates the air inside the car, putting less strain on the AC. However, at high speeds, the rapid air flow makes prolonged use of internal circulation stuffy, affecting comfort and increasing fatigue. My approach is to use external circulation for fresh air in areas with good air quality, like rural highways, and switch to internal circulation in urban or polluted areas. Over time, a clogged AC filter can reduce airflow, so regular cleaning is necessary. In short, a balanced approach is most cost-effective.

[KhloeRose]

When I first started driving, I misused the recirculation mode on the highway. Later, I learned that the recirculation mode is suitable for short highway trips, such as within half an hour, as it helps maintain a cool or warm temperature inside the car without constantly adjusting the air conditioning. However, for long-distance highway drives exceeding an hour, it's essential to switch to the fresh air mode; otherwise, the air inside may become stale, potentially causing dizziness. Check the external environment: if there's no smoke or dust, use the fresh air mode; if there are unpleasant odors, switch to recirculation to save energy. Also, don’t forget regular maintenance of the air conditioning system to ensure a safe and reliable experience on the highway.