Is Idling Harmful to a Car?

[MacElizabeth]

If a car is left idling for a short period, it will not cause any damage. However, prolonged idling can lead to carbon buildup in the engine, which is a result of incomplete combustion. Therefore, it is recommended not to leave the car idling for extended periods. When a car idles, incomplete combustion occurs in the engine, leading to carbon deposits. These deposits can cause engine knocking, which is an abnormal combustion phenomenon. During the compression stroke of the engine, the piston moves upward, compressing the air-fuel mixture. This increases the pressure and temperature of the mixture. If the mixture ignites spontaneously at this point, it results in knocking. The burning mixture pushes the piston downward while it is moving upward, affecting the engine's power output and fuel efficiency. Due to the low engine speed and reduced air intake efficiency during idling, combustion is inherently incomplete, making it easier for carbon deposits to form. More importantly, these deposits cannot be expelled and accumulate in the cylinders and intake passages, significantly speeding up the carbon buildup process. When carbon deposits reach a certain level, they can reduce the car's performance and, over time, lead to engine wear. During idling, the car does not perform any external work—the engine only overcomes its own internal resistance. Thus, it is advisable to turn off the engine during prolonged waits.

[DeJuniper]

I believe that prolonged idling is indeed harmful to cars. As someone who has driven for many years, my experience shows that at idle speed, the engine runs at low RPM with incomplete combustion. Over time, this easily leads to carbon buildup clogging fuel injectors and valves, resulting in reduced power and increased fuel consumption. Especially during urban traffic jams, many people habitually idle while waiting, but older cars suffer particularly badly, requiring regular part cleaning and increased maintenance costs. I've tried turning off the engine at red lights or limiting warm-up idling to under one minute when starting – the car runs much smoother this way. Additionally, idling drains the battery, which could cause trouble during cold winter starts. Overall, minimizing idling can extend a car's lifespan. Keeping the engine moving through driving is actually beneficial and can save on fuel and maintenance costs.

[VanKathryn]

From an environmental perspective, idling is truly detrimental. As someone who practices green driving, I'm aware that idling emits large amounts of exhaust, including carbon dioxide and pollutants, directly impacting air quality—especially in densely populated areas. Prolonged idling is essentially running the engine for nothing, being neither energy-efficient nor environmentally friendly. Many major cities have regulations prohibiting extended idling; for instance, leaving your engine running while parked could result in fines. I make it a habit to turn off the engine when waiting in parking lots or use mobile apps to monitor my vehicle's status. This reduces my carbon footprint and benefits the climate. Engines operate inefficiently and experience greater wear during idling, so I recommend cultivating this habit—it's good for both the planet and vehicle maintenance.

[Tammy]

As a car owner who frequently keeps track of expenses, I find that idling is purely a waste of money. The engine burns fuel without moving, essentially wasting a liter of fuel that could have been used productively, leading to significant additional monthly costs. Idling for an hour consumes fuel equivalent to driving dozens of kilometers, literally throwing money away. Moreover, excessive carbon buildup leads to expensive repairs—fixing a fuel injector alone can cost hundreds. I’ve tried reducing idle time, such as turning off the engine while waiting briefly and using only the fan or ventilation instead of the AC, or simply shutting off the engine to save money. In summer, idling with the AC on causes an even more noticeable spike in fuel consumption. In short, from an economic standpoint, idling is absolutely not recommended—the money saved can be better spent on fuel or maintenance.