Does a car consume fuel when idling without turning off the engine?

[McVincent]

Leaving a car idling without turning off the engine will definitely consume fuel. The following are the hazards of idling without turning off the engine: 1. When the engine speed is very low, the intake vortex weakens, resulting in poor fuel atomization and incomplete combustion of the fuel. Additionally, at low engine speeds, valve leakage and piston ring leakage increase. Combined with the extended contact time between the combustion gases and the cylinder walls, heat dissipation losses increase, leading to higher fuel consumption. 2. During idling, the engine oil pressure is relatively low, worsening the lubrication conditions of moving parts. Unburned fuel washes the cylinder walls, and incomplete combustion can easily lead to carbon deposits. These factors accelerate the wear of moving parts. Moreover, when the coolant temperature drops below 60 degrees, combustion byproducts in the cylinders may react chemically with moisture, forming acids that increase cylinder corrosion.

[Lilah]

Hey, when it comes to whether keeping the engine running consumes fuel, I have to start with my daily experience. After driving for so many years, idling the engine while waiting by the roadside or in traffic definitely burns fuel, though less than when driving. For example, I often wait for family outside the supermarket, and idling for ten minutes burns about 0.2 liters of fuel, which adds up to a little over a yuan. Over time, small amounts accumulate. Last month, I idled for half an hour waiting for someone, and the fuel gauge dropped noticeably. Not to mention idling with the AC on in summer consumes even more—about two liters per hour. So now I’ve developed a habit: it’s fine not to turn off the engine for short waits, but if it’s over five minutes, I shut it off. It saves fuel and reduces emissions. In the long run, it helps avoid engine carbon buildup and saves a bit of money. I think most drivers have encountered this situation, and being more conscious about it doesn’t hurt.

[McWalker]

From an environmental perspective, keeping the engine idling without turning it off definitely wastes fuel and resources. I know that as long as the engine is running, it's burning gasoline and releasing carbon dioxide, polluting the air. Idling for an hour is equivalent to wasting a liter of fuel, and the emissions are significant, especially when queuing in urban parking lots. I've seen many cars idling for long periods while waiting, neither turning off nor moving, and the cumulative waste has a major impact on air quality. That's why I always encourage everyone to turn off the engine when parked to reduce unnecessary emissions. This not only saves you money but also contributes to social environmental responsibility. Idling noise is also an annoyance. In short, changing this small habit can improve overall efficiency.

[JoyRose]

Here's how I understand car idling: Keeping the engine running at idle inevitably consumes fuel, as the engine operates at its minimum speed to maintain system functionality. A typical sedan consumes about 1-2 liters of fuel per hour at idle, with air conditioning or heating increasing this consumption. However, idling uses significantly less fuel compared to driving – for instance, driving for an hour might consume around ten liters, while idling only uses one or two liters. Therefore, brief stops don't consume much fuel, but prolonged idling leads to considerable waste. Personally, I assess situations pragmatically: waiting a few minutes with the engine running is acceptable, but I always turn off the engine if idling exceeds ten minutes. This approach ensures both safety and resource conservation.