Should You Use External or Internal Air Circulation on the Highway?
2 Answers
When driving on the highway, it is recommended to use the external air circulation mode for the air conditioning. The reasons for using external air circulation on the highway are as follows: 1. Highway: When driving on the highway, the windows are usually closed, preventing air circulation inside the vehicle. Turning on external air circulation allows outside air to enter the cabin, improving air freshness. 2. Air Conditioning: External air circulation has minimal impact on air conditioning efficiency during high-speed driving, whereas using it in daily driving may reduce cooling effectiveness. 3. Windshield: Fogging on the windshield is mainly caused by excessive humidity inside the cabin. External air circulation continuously supplies fresh air, maintaining optimal humidity levels and reducing the likelihood of fogging.
I prefer using the external air circulation mode on highways. During long-distance drives, the biggest fear is drowsiness, and the external circulation allows fresh air to continuously flow in, which keeps me much more alert than being stuffy with the internal circulation on. Even with the AC on in summer, there's no need to worry—modern cars come with automatic adjustment features, so the cooling effect remains good. However, when I see heavy truck exhaust or pass through tunnels, I immediately switch to internal circulation for a while. Another benefit of external circulation is preventing window fogging, especially on rainy days with high humidity. Basically, I use external circulation for 90% of my highway trips, only switching to internal circulation entirely during sandstorms or heavy smog.
