Should You Use External or Internal Air Circulation in the Car During Winter?
3 Answers
In winter, you can use either internal or external air circulation for the car's heating system, depending on the specific situation. The details are as follows: 1. If you want to heat the car quickly in winter, you can start the engine and drive normally for a while to warm it up. Once the temperature gauge needle reaches the middle position, turn on the internal air circulation for heating. Using internal circulation allows the air conditioning to rapidly cool or heat the car interior. This not only warms the car quickly but also avoids putting extra load on the engine, saving fuel. 2. However, although continuous internal circulation keeps the car warm, it creates a relatively sealed indoor environment. Prolonged exposure to this environment can lead to oxygen deprivation. Therefore, it's best to switch to external circulation every hour to draw in fresh air from outside. This air is then passed through the air conditioning evaporator or heater core to produce cold or warm air, respectively.
Driving in winter with a foggy windshield is so frustrating! Last time I drove in the morning, the glass was completely white, and the wipers couldn’t even move. A mechanic taught me to first turn on the external air circulation for a few minutes to ventilate, then switch to internal circulation for heating—the fog disappeared instantly. Later, I also discovered a trick: when parked and waiting, using internal circulation saves fuel, but on the highway, you need to switch to external circulation every half hour to get fresh air, or you’ll feel dizzy from the stuffiness. Oh, and in sub-zero weather, defrosting requires turning on external circulation to blow air at the windshield—mixing warm air with a bit of cold air speeds up the process. I’ve been using this method for three years and haven’t needed to wipe the glass with a cloth since.
Seasoned drivers know the tricks for air circulation in cars during winter. My routine is to start the engine, roll down the windows for 30 seconds to vent exhaust fumes, then switch to fresh air mode to let the AC draw in cold outside air for heating. But avoid this on slushy days! Exhaust vapor mixed with cold air will instantly frost your windshield. Last year during a snowstorm traffic jam, I used recirculation mode for warmth but ended up with condensation-fogged glass after two hours. Now I've learned: use recirculation for quick heating on short trips, fresh air mode for long drives. Here's a pro tip - turning off the AC when using heater saves fuel, but you'll need AC for defogging when windows mist up.
