In winter, should the car's heating system use internal or external air circulation?

[OBenjamin]

In winter, whether to use internal or external air circulation for the car's heating system depends on the actual situation: 1. To quickly heat up the car interior in winter, you can first start the engine and drive normally for a while to warm up. When the temperature gauge needle reaches the middle position, turn on the heating with internal circulation. Using internal circulation allows the air conditioning to quickly cool down or heat up the car interior. This not only warms up the car quickly but also does not burden the engine and is more fuel-efficient. 2. Although continuous internal circulation keeps the car warm, as the car interior forms a relatively sealed environment, prolonged exposure can easily lead to oxygen deprivation. Therefore, it's best to switch to external circulation every hour to draw in fresh air from outside.

[Timothy]

In winter when using the car heater, I always prioritize the fresh air intake mode (external circulation) as it brings in fresh air and prevents window fogging. Last time during a long drive, I used recirculation mode for too long, causing high humidity inside the car. The windows fogged up severely, nearly obscuring the road view - extremely dangerous. Since then, I first use recirculation mode for a few minutes after starting to warm up faster, then immediately switch to external circulation to maintain air flow. This not only prevents drowsiness from CO₂ buildup but also improves air quality, especially beneficial for children and elderly passengers' respiratory health. However, in extremely cold conditions, external circulation may let cold air in - I recommend increasing heater temperature to compensate. Overall, safety comes first - a balanced mix of both modes ensures clear visibility and comfortable driving.

[DiAmelia]

As someone who prioritizes energy efficiency, I tend to use the recirculation mode more often when the heater is on in winter, as it helps retain heat inside the car, reduces the heater's energy consumption, and saves fuel and money. Every time I switch to fresh air mode, cold outside air enters, forcing the heater to work harder again, which wastes fuel. However, I've noticed that prolonged use of recirculation leads to stuffy air and increased fogging issues. So, I've adopted a compromise: use recirculation initially for rapid heating, then briefly switch to fresh air mode every 15 minutes once the cabin temperature stabilizes to refresh the air. On rainy days with high humidity, I switch to fresh air mode to prevent fogging, while on dry days, I prioritize recirculation for heat retention. This approach saves resources while maintaining comfort.

[StellaRose]

I think the car's heating system should alternate between recirculation and fresh air modes in winter. Recirculation heats up the cabin quickly but can lead to air pollution and fogging; fresh air mode provides ventilation to reduce humidity and prevent fogging, though it initially cools the interior. My usual practice is to start with 5 minutes of recirculation to warm up, then switch to fresh air for 10 minutes, repeating this cycle. With more passengers, fresh air becomes more crucial to prevent oxygen deprivation. During rain or snow, fresh air mode is particularly important to maintain clear visibility, which gives me greater driving confidence.