Is It Okay to Idle the Car with AC On for Two Hours?

[DiLaura]

Yes, but idling the car with AC on can be harmful to the vehicle. Prolonged idling with the AC running increases fuel consumption and accelerates the formation and retention of carbon deposits in the engine. If the car is parked in a poorly ventilated area or inside a garage, occupants may also be at risk of carbon monoxide poisoning. Hazards of idling: Idling can lead to oil burning: During idling, the throttle opening is small, and the vacuum level inside the intake manifold is high, which can draw oil vapor into the intake manifold. Some of this oil vapor deposits inside the intake manifold, forming carbon-like substances or coking. Extended low-speed driving or idling, especially in turbocharged models, may result in a pool of oil inside the intake manifold behind the throttle body. However, this oil usually disappears after highway driving. Idling promotes carbon buildup: During idling, the air-fuel mixture tends to be richer, which can lead to engine carbon deposits over time. Similarly, stop-and-go driving at low speeds, such as frequent acceleration and braking, can also cause carbon buildup as the engine alternates between rich and lean fuel mixtures.