Should the car air conditioning be set to internal or external circulation in winter?

[JoyMarie]

In winter, it is recommended to use both internal and external circulation for the car air conditioning. First, set the air conditioning to internal circulation mode to quickly raise the temperature inside the car. Once the interior feels warm, switch to external circulation to promote air flow. The optimal temperature setting for the heater is 23 degrees Celsius. Additionally, adjust the air vent direction to avoid blowing directly at the face, as this can cause fatigue and affect driving safety. Instead, direct the airflow towards the legs and feet; warming these areas will help warm the entire body. The AC button controls the air conditioning compressor. Pressing this button activates the compressor, which increases fuel consumption. The compressor's primary function is to provide cooling. It's important to note that the car's cooling and heating systems are separate. The heating system utilizes the vehicle's own heat cycle and does not require the compressor to operate.

[SanLondon]

I think using the air conditioning in winter requires a flexible approach. When you first get in the car and it's as cold as an ice cellar, turning on the recirculation mode heats up the cabin fastest and saves fuel. However, don't keep it on continuously - prolonged use makes the air stuffy as CO₂ levels rise, which can cause drowsiness and compromise driving safety. My routine is to switch to fresh air mode for a few minutes every twenty minutes after the cabin warms up. This maintains air freshness without significant temperature drops. Also remember: if windows fog up, immediately activate fresh air mode with AC dehumidification - it works instantly.

[VanBarrett]

In winter, what I value most when using the air conditioning is comfort. It's indeed cozy to use the recirculation mode when the car is just warming up, but after a while, my nose and throat get uncomfortably dry. Switching to fresh air mode provides more humid air and easier breathing, but the cold drafts can make me shiver. So, I take a balanced approach: set the temperature around 22°C, first use recirculation to warm up the car, then switch to fresh air once I'm comfortably warm. Especially when sleeping with the heater on, I must use fresh air mode to ensure proper air circulation. This way, throughout the entire journey, I neither freeze nor feel stuffy.

[MacGrant]

Fifteen years of driving experience taught me that using the AC in winter depends on road conditions. In city traffic jams with heavy exhaust fumes, avoid using the external air circulation to prevent inhaling car exhaust. On highways, external circulation is better—it improves airflow and saves fuel. However, never use internal circulation on rainy or snowy days, as exhaled moisture can't escape, causing the windshield to fog up instantly—very dangerous! I prefer using automatic AC, which intelligently switches between internal and external circulation. Drivers without automatic AC should keep a dry towel handy to wipe fogged-up windows.

[BrynleeMarie]

My principle is to stay both warm and healthy. Although using the recirculation mode heats up the car faster, it tends to accumulate harmful substances like formaldehyde, especially in new cars, so extra caution is needed. I usually switch to the fresh air mode once the car warms up. It might consume a bit more fuel, but it's better for your health. Here's another tip: don't turn off the A/C button when using the air conditioning. Even though you don't need cooling in winter, this button activates the compressor's dehumidification function, which, when combined with the fresh air mode, helps prevent fogging. If you're really afraid of the cold, getting a fleece seat cover is very effective. When your body is warm, you naturally don't need to turn the air conditioning up too high.

[MacLogan]

Here's how I operate: In the morning, I start the vehicle and immediately turn on the recirculation mode. I wait until the coolant temperature warning light goes off before turning on the heater, which ensures the most efficient warming. During long-distance driving, I pay special attention to air humidity—I switch to fresh air mode for ten minutes every hour to effectively prevent fatigue driving. When encountering poor outside air quality, such as passing through construction sites or areas with many trucks, I immediately switch back to recirculation mode. Additionally, I remind everyone to regularly replace the cabin air filter, as it tends to accumulate dust easily in winter. A dirty filter can worsen the air quality inside the car. Using the air conditioning this way is both fuel-efficient and safe, and I’ve personally tested its effectiveness.