Should You Turn Off the Engine While Waiting in the Car?

[DeclanLynn]

If the waiting time is less than five minutes, you can keep the engine running; however, if it exceeds five minutes, it is advisable to turn off the engine. Otherwise, apart from wasting fuel and increasing engine carbon deposits, sitting in the car for an extended period while waiting not only consumes more fuel but also poses safety hazards. This is because the carbon monoxide content in car exhaust is extremely high. Prolonged idling while waiting can easily lead to carbon monoxide poisoning if not careful, especially in underground parking lots where it is crucial to avoid idling for too long. The hazards of prolonged idling are as follows: 1. Due to extended idling, the engine temperature remains too low, leading to incomplete fuel combustion, which can cause carbon buildup, clog the fuel injectors, and severe carbon deposits may even cause the piston rings to seize or break. 2. During prolonged idling, poor fuel atomization can result in unburned atomized diesel condensing and washing down the cylinder walls, entering the lubricating oil and diluting it, thereby accelerating engine wear as the moving parts do not receive adequate lubrication. 3. Poor combustion during prolonged idling worsens engine emissions. If toxic gases enter the cabin, occupants may face the risk of suffocation. Additionally, the release of toxic gases pollutes the environment. Some countries have traffic regulations that prohibit prolonged idling (limited to 3-5 minutes) when parking on the roadside, with fines enforced by traffic police for violations. 4. Low idle speed reduces the oil pump speed, leading to low oil pressure and insufficient lubrication at critical points. 5. While the engine maintains a constant internal operating temperature, components like the exhaust manifold and catalytic converter rely on airflow for cooling. Prolonged idling can hinder heat dissipation in high-temperature engine parts and may even damage the catalytic converter due to excessive heat. Generally, it is best not to let the engine idle for more than 10 minutes.

[JonathanAnn]

As a long-distance driver, whether to turn off the engine while waiting depends on how long the stop is. If it's just a minute or two, turning off and restarting the engine might actually consume more fuel due to the high fuel consumption during ignition. However, if the wait exceeds three minutes, I always turn off the engine. Many people might not know that idling not only burns fuel but also increases engine carbon deposits. Once, I idled for ten minutes without turning off the engine, and the next day, the engine shook badly. The mechanic said it was due to carbon buildup. The most frustrating situation is waiting with the air conditioning on in summer. I once idled for half an hour at the airport waiting to pick someone up, and the fuel gauge dropped rapidly—it was heartbreaking. Now, I bring a book and wait outside the car, saving fuel and protecting the car. Waiting for twenty minutes only consumes a few minutes' worth of fuel.

[Dawson]

With a decade of auto repair experience, I recommend turning off the engine if idling exceeds 60 seconds. During idling, the engine maintains around 800 RPM. While it runs smoothly, insufficient fuel pump pressure can easily lead to clogged fuel injectors. Especially in winter when warming up the car while waiting, the white smoke is carbon particles from incomplete combustion. The most extreme case I've seen: a BMW owner idled for an hour daily waiting for their child at school, resulting in a $30,000 engine overhaul after six months. Modern cars with start-stop systems avoid this issue as the system automatically determines when to shut off. If concerned about starter wear, using genuine full-synthetic oil significantly reduces wear, allowing hundreds of start-stop cycles without problems.

[SanAdalynn]

Last time I was waiting for my wife to finish her check-up at the hospital entrance, I specifically looked up the information. A regular 1.6L model consumes 1-2 liters of fuel per hour at idle, which translates to about eight to fifteen yuan at current fuel prices. However, safety is more important. If it's dark or in an area with poor security, I'd rather burn a bit more fuel than turn off the engine, keeping the headlights on to deter anyone with ill intentions. Once, while waiting for someone at a suburban gas station, the attendant came over and informed me that new regulations require the engine to be turned off. That's when I learned many cities impose a 200-yuan fine for idling in public places for more than three minutes. Now I've developed the habit of shifting to P gear and pulling the handbrake, which prevents the car from rolling and avoids the fuel consumption triggered by auto-hold.

[VonElaina]

Hybrid cars are the best for waiting situations. After parking, I simply switch to pure electric mode, and running the air conditioning for half an hour only consumes 1% of the battery. For traditional fuel-powered cars, the "30-second rule" in summer is quite practical: if the temperature outside is higher than inside with windows open, keep idling with AC on; otherwise, turn off the engine and open the windows. Last week at a scenic spot parking lot, I noticed an interesting phenomenon: dozens of cars were queuing to pick up tourists, and about 90% had their engines off with windows open while waiting. I asked a CR-V owner, who said he had tested that idling with AC on while waiting consumes more fuel than restarting the engine, but if the wait exceeds six minutes, the opposite becomes true. This tipping point duration varies by model—check your vehicle's manual; my Japanese car specifies three minutes.