Should the air conditioning be set to internal or external circulation when driving on the highway?

[Emmett]

When driving on the highway, it is recommended to set the air conditioning to external circulation. The reasons for using external circulation on the highway are as follows: 1. When driving on the highway, the windows are usually closed, preventing air circulation inside the vehicle. Turning on external circulation allows outside air to enter the car, improving air freshness inside. 2. During high-speed driving, external circulation has minimal impact on the air conditioning's effectiveness, whereas using it in daily driving may reduce efficiency. 3. Windshield fogging is mainly caused by excessive humidity inside the car. Turning on external circulation continuously introduces fresh air, maintaining moderate humidity levels inside and reducing the likelihood of fogging.