Should You Use Internal or External Air Circulation in the Car During Summer?

[NicoleRose]

In summer, first use the external air circulation or open the windows to ventilate, then switch to internal circulation. More information about internal and external air circulation is as follows: 1. Internal circulation can enhance the effectiveness of the air conditioning, essentially recirculating the cooled air inside the car. However, prolonged use of internal circulation can degrade the air quality inside the car, potentially causing dizziness or discomfort. It's advisable to use internal circulation for a while and then switch to external circulation for a few minutes to allow fresh air to enter and improve air quality. If the air conditioning's internal/external circulation switch is a mechanical lever rather than a button, you can position the lever in the middle to allow a moderate amount of outside air to enter, thereby enhancing air quality. 2. External circulation allows you to breathe fresh air from outside the car. In winter, if the warm air feels too hot, you can turn off the fan and switch to external circulation to maintain the interior temperature while still getting fresh air.

[StBeau]

In summer, I usually start with the air recirculation mode when driving, which cools the car down super fast—it gets nice and chilly the moment I get in. The recirculation mode just cycles the air inside the car, keeping the hot outside air out. For short trips, like a 10-minute commute, it’s super convenient. But if you keep it on too long, the air inside gets stuffy, and you might feel drowsy. So, I recommend switching back to fresh air mode after about 20 minutes to let some outside air in. I always do this on long highway drives—it keeps me comfortable, alert, and avoids that dizzy feeling from too much CO2 buildup. Also, remember to clean or replace the cabin air filter regularly, or dust buildup can reduce efficiency. Since the temperature difference between inside and outside is big in summer, switching modes doesn’t waste fuel and helps the AC run smoother.