Will leaving the car running for 8 hours without turning it off cause any damage?

[AbelFitz]

This won't cause any significant damage to the car, but it will increase carbon deposits in the engine. When the car's engine is idling, the combustible air-fuel mixture cannot burn completely, so prolonged idling will lead to increased carbon buildup in the engine. Here are the reasons why the car might not start with one push of the button: 1. Excessive carbon deposits: This could be caused by too much carbon buildup in the idle speed control valve, intake tract, intake valves, or combustion chamber. 2. Too rich or too lean air-fuel mixture: Due to excessive carbon deposits or dirt in the intake tract, the cross-sectional area of the air passage changes, resulting in an overly rich or lean mixture, causing abnormal combustion or engine shaking after startup, or even failure to start. Alternatively, it could be due to issues with the fuel injectors, such as leaks or excessive carbon deposits, leading to a lean mixture during startup and difficulty starting. 3. Faulty carbon canister or carbon canister solenoid valve: Malfunctions in the carbon canister or its solenoid valve can also cause difficulty starting.

[SanAshlyn]

I've been driving for twenty years, and in the early years, I also experienced forgetting to turn off the engine. Once, I parked in the company parking lot in the morning without shutting off the engine, and when I got off work in the evening, I found the car was still running—a full eight hours without stopping. The most direct impact was a sudden surge in fuel consumption. Idling for an hour wastes about a liter of fuel, so I estimated I burned through ten liters unnecessarily, costing over a hundred yuan. Prolonged engine idling also increases component wear, such as more intense friction between piston rings and cylinder walls, faster degradation of lubricating oil, and potential buildup of more carbon deposits that affect performance. Although modern cars are designed to be sturdy and generally won’t break down immediately, frequent idling like this can shorten the vehicle’s lifespan. After that incident, I developed a habit of turning off the engine as soon as I exit the car and confirming the dashboard lights are off before locking the door. Additionally, safety is a concern, especially in garages or enclosed spaces, where excessive carbon monoxide from exhaust fumes can pose a poisoning risk.

[StAdalynn]

Last time I was in a hurry for an appointment and forgot to turn off the engine when parking. Eight hours later, I returned to find the car still idling there. The fuel gauge showed nearly one bar less, which made my wallet ache—calculating the loss, it was several tens of dollars. I asked a mechanic, who said it was no big deal, with engine wear being minimal, similar to driving for a whole day. However, if it were an old car or a manual transmission, it might accelerate aging, putting more pressure on the lubrication system. Fortunately, I parked in an open area with good ventilation, so there was no risk. Since then, I often remind myself not to be careless—adding a phone alarm that rings when I exit and lock the door has been quite practical. Daily drivers shouldn’t worry too much; one or two incidents won’t affect safety, but fuel waste is the most immediate concern. Developing good habits saves both peace of mind and money.

[AryaFitz]

The main issues with idling the engine for eight hours are fuel consumption and accumulated wear. Continuous movement of the piston group with poor lubrication can easily wear out parts and may increase carbon buildup, clogging the fuel injectors. Although the battery is charged by the alternator and remains fine, the high fuel consumption wastes resources. It is recommended to check the oil level to ensure it is normal. Forgetting once is not serious, so don't worry.

[Rita]

From an economic perspective, forgetting to turn off the engine for eight hours is purely a money-burning game. At an average idling fuel consumption of 1 liter per hour, eight hours consume 8 liters of fuel, which at 8 yuan per liter equals 64 yuan gone. The minor engine wear and potential repair costs of a few hundred yuan aren't a big deal. But with poor habits leading to repeated instances, the losses can double—better to save that money for travel. I always remind myself to turn off the engine when getting out of the car.

[HavenDella]

Forgetting to turn off the engine for eight hours has serious environmental and safety consequences. Continuous exhaust emissions from the engine pollute the air, exacerbating smog issues especially in urban areas. In enclosed garages, the accumulation of carbon monoxide poses a deadly risk, and it also makes the car a target for thieves. As someone who frequently focuses on emission reduction efforts, I've developed the good habit of turning off the engine immediately after parking—beneficial for both the planet and people.