Is it better to use the car air conditioner in recirculation mode or fresh air mode?

[CalebFitz]

Car air conditioning should be used flexibly according to actual conditions: 1. Consider road conditions: Use fresh air mode on highways. Due to wind resistance and high speed, it's not suitable to open windows on highways. Prolonged use of recirculation mode may cause hypoxia in the brain, affecting reaction and judgment, which is very dangerous. Additionally, air quality on highways is generally good with low exhaust concentration, making fresh air mode preferable. In crowded urban areas or during rush hours when vehicle exhaust concentration is high, switch to recirculation mode decisively. 2. Consider vehicle condition: New cars contain high concentrations of toxic gases like formaldehyde. For the first 3-6 months after purchasing a new car, it's recommended to use fresh air mode along with opening windows to enhance air circulation and dilute toxic gas concentrations. 3. Consider air quality: In areas with severe PM2.5 pollution (above 50) where air quality isn't good, use recirculation mode to avoid excessive inhalation of PM2.5 particles into the lungs.

[StZane]

There's no absolute answer to this question, it depends on the situation. When I first bought my car, I also struggled with this. Later, I found that turning on the recirculation mode can block exhaust fumes and dust from entering the car when stuck in traffic or passing through dusty areas. However, keeping the recirculation mode on for too long increases the carbon dioxide concentration inside the car, making it easier to feel drowsy. On highways, I prefer using fresh air mode, especially during rainy days when it's particularly effective at defogging. Once, I kept the recirculation mode on for three hours straight and felt dizzy when getting out of the car. Now, I start with 10 minutes of fresh air mode to refresh the air when I get in the car, then switch to recirculation to maintain cooling once the temperature drops. In tunnels with poor air quality, I manually switch between modes as naturally as breathing.

[LillianaRose]

It depends on what you prioritize. For quick cooling, using the recirculation mode is most effective as it seals the hot air inside the car, making the AC cool much faster. However, during heavy smog in our area, recirculation can actually increase the PM2.5 concentration inside the car. Once, a test showed it was 40% higher than outside. After parking under the scorching sun in summer, I first open the windows for two minutes to ventilate before turning on the AC, using the fresh air mode to expel the hot air, then switch to recirculation once the temperature drops. The key is to monitor the air quality index closely; when the air is poor, even if it consumes more fuel, using the fresh air mode is necessary.

[OEloise]

Fuel-saving advocates recommend using the recirculation mode more often. Experimental data shows that the air conditioning compressor load is 10%-15% lighter when using recirculation mode, especially noticeable during traffic jams. However, it's worth reminding you: using fresh air mode is more comfortable when heating in winter, as it prevents dry mouth and throat. Once during winter, I used recirculation mode continuously for four hours, and the windshield fogged up extremely quickly on the inside - the wipers couldn't even clear it. The most stable approach is to use AUTO mode. Nowadays, even moderately good cars can automatically switch between air circulation modes, which is much more convenient than manual adjustment.