Use Internal or External Air Circulation in Winter?

[MatthewLynn]

Correct practice is to alternate between internal and external air circulation in winter. Below is more information about air circulation modes: Brief description: Internal circulation means the AC system closes external air intake and only recirculates air inside the vehicle cabin. External circulation means the AC system opens to draw fresh air from outside the vehicle. Benefits of alternating use: Faster cooling/heating effects from AC system, prevents excessive CO2 concentration, maintains oxygen levels (low oxygen causes drowsiness and driving risks), keeps cabin air clean, and maintains good cabin environment.

[DelCollin]

As a health-conscious car owner, I definitely prefer the fresh air mode (outside air circulation) when driving in winter. Although the recirculation mode can quickly warm up the cabin by recycling interior air, it leads to reduced oxygen levels and accumulated carbon dioxide over time - which can easily cause dizziness and drowsiness for occupants. This isn't good for either the driver's or passengers' health. Especially when carrying multiple passengers, the risk of stale air and bacterial growth increases, requiring extra vigilance during flu season. In contrast, fresh air mode brings in outside air to replenish oxygen and dilute impurities, improving air quality and preventing illness. Winter air tends to be dry, and the fresh air mode also helps remove moisture to prevent window fogging, ensuring clear visibility. I typically use recirculation for a few minutes when first starting a cold engine to warm up, then switch to continuous fresh air mode once normal temperature is reached. Overall comfort and health are top priorities, so I recommend relying more on fresh air mode during winter to create a safer cabin environment.

[MacTheo]

From a safety perspective, it's essential to use the external air circulation more often when driving in winter. While turning on the internal circulation heats up the car faster, the fatal issue is that the windows are prone to fogging up. Thick fog severely obscures visibility and can easily lead to accidents, especially during rain, snow, or at night. External circulation, however, introduces cold air from outside, effectively dehumidifying and reducing the humidity inside the car to prevent fog formation. Just think about how dangerous it is when fog blocks your view while driving on the highway—this is far more important than saving a bit of warm air. I usually start with internal circulation to warm up the car for about five minutes, then immediately switch to external circulation and keep it running. If fog appears, turning up the heater along with external circulation can clear it faster. Safety always comes first, and this small habit has helped me avoid multiple potential hazards. Make sure to develop this awareness in winter.

[LeAnastasia]

With a focus on saving money and efficiency, I prioritize using the external circulation mode in winter. While internal circulation can quickly warm up the car, it often leads to window fogging, forcing me to turn on the defogger, which increases additional fuel consumption—more loss than gain. External circulation, despite introducing cold air and slowing down the heating process, helps maintain dryness and reduces the need for defogging, ultimately saving more fuel and energy in the long run. I remember testing it for a whole month, and the combined fuel consumption with external circulation was 10% lower than with internal circulation, a significant difference during winter commutes. At startup, I briefly use internal circulation to warm up the car, then switch to external circulation once the temperature rises to prevent moisture and energy waste. This strategy not only protects the engine but also saves money—a win-win. I highly recommend this approach for daily driving.