Is it okay to leave the engine running with the air conditioning on while parked?

[SebastianLee]

It is possible to leave the engine running with the air conditioning on while parked, but it is not recommended to do so for extended periods. When the car is idling with the air conditioning on, the engine needs to overcome the internal friction resistance of its components without delivering power externally. This leads to incomplete fuel combustion, which can cause carbon deposits to accumulate in the cylinders and on the throttle valve. Additionally, during idle operation, the incomplete combustion of fuel results in exhaust gases containing high levels of carbon monoxide. This carbon monoxide can accumulate around the vehicle and may enter the cabin through the air conditioning system. With the windows closed while the air conditioning is on, the lack of air circulation can cause the concentration of carbon monoxide inside the car to rise over time.

[OKarter]

As for idling with the AC on, I personally think it's no big deal to do it occasionally—like when waiting for someone roadside for about ten minutes to cool off comfortably. However, prolonged idling can cause issues: the engine keeps running and wasting fuel, burning roughly a liter per hour, which hurts the wallet. If parked in an underground garage or enclosed space, exhaust fumes can accumulate, posing health risks. So, I usually only do it briefly when urgently needed. If exceeding 15 minutes, it's wiser to turn off the engine and roll down the windows—more fuel-efficient and much safer. Developing good habits can extend the car's lifespan and be more eco-friendly.

[KinsleyAnn]

To be honest, I'm more concerned about the health risks of running the AC while parked. The engine emits carbon monoxide, a colorless and odorless gas, which becomes dangerous if it seeps into the car when ventilation is poor, such as when parked in a home garage or in the middle of traffic. Once during summer, I left the engine running for shopping comfort and ended up dizzy and nauseous after half an hour—turns out it was mild carbon monoxide poisoning diagnosed at the hospital. Since then, I limit AC use to just 3-5 minutes when parked and always crack a window for ventilation. Life is priceless, folks—safety first, don't let convenience turn into harm.

[MaliaAnn]

From a car maintenance perspective, leaving the engine running with the AC on while parked is actually quite harmful to the vehicle. Prolonged engine idling can lead to severe carbon buildup due to low load conditions, affecting engine performance. Additionally, the battery must support the power consumption of the AC system, and if the battery is low, it may cause starting difficulties. Fuel consumption also increases significantly, burning about 0.5-1 liters per hour, which is simply a waste of money. Therefore, I recommend avoiding this practice for extended periods. Short durations, such as waiting at a red light, are acceptable, but don't make it a habit. Turning off the engine promptly can reduce wear and help maintain better vehicle condition for longer durability.