What are the consequences of leaving the car running for five hours without turning it off?
4 Answers
Leaving the vehicle running without turning it off for an extended period can lead to the following consequences: 1. The engine remains in a low-speed operating condition; 2. The pistons and valves are more prone to carbon buildup, which can result in unstable idling and other adverse effects on the engine's power performance, and may even impact the engine's service life. Additional information: The three-way catalytic converter may not reach its operating temperature, which can affect its lifespan. Most vehicle models are equipped with a three-way catalytic converter in the exhaust system. This is the most important external purification device for vehicle exhaust, converting harmful gases such as CO, HC, and NOx emitted from the exhaust into harmless carbon dioxide, water, and nitrogen through oxidation and reduction. Prolonged idling with the air conditioning on makes it difficult for the three-way catalytic converter to reach the appropriate operating temperature, reducing its exhaust treatment capability and negatively affecting its lifespan.
I've been driving for half my life, and this is a common occurrence. The most obvious issue with leaving the engine running for five hours is the fuel consumption. Idling for an hour burns at least one or two liters of fuel, which adds up to a significant cost at current fuel prices. When the engine runs at low speeds for extended periods, incomplete combustion is particularly prone to causing carbon buildup, which clogs the spark plugs and throttle body. You'll notice shaking and lack of power the next time you start the car. The tailpipe continuously emits hot air, which can scorch nearby leaves and leave oil stains on the ground. Continuous operation of the air conditioner puts excessive load on the compressor, and parking in an enclosed garage can easily lead to carbon monoxide poisoning. I've seen cases where this drains the battery completely, requiring a rescue vehicle. Older cars need to be especially careful with the cooling system, as insufficient radiator circulation can lead to engine seizure. Leaving the heater on all night in winter can also easily cause frost to form on the windows.
Yesterday my friend forgot to turn off the engine while binge-watching shows in the car, and the fuel gauge dropped two notches in just one day. Five hours of idling consumes fuel equivalent to driving 100-180 kilometers for nothing – what a painful hit to the wallet. Long-term low-RPM operation causes insufficient piston temperatures, leading to carbon deposit buildup that gradually results in unstable idling and black exhaust smoke. The exhaust pipe under the car glows red-hot – imagine if it scalded a passing puppy. The battery relies on the alternator for charging, so repeatedly draining it without recharging drastically shortens its lifespan. In summer, prolonged AC use strains the blower motor bearings, often causing abnormal noises. Worst of all, this pointless idling needlessly pollutes the environment with wasted emissions.
Back when I was driving for ride-hailing, this kind of thing happened often. Idling continuously for five hours thickened the engine oil, reducing lubrication and accelerating wear. Keeping the engine at operating temperature sped up the thermal aging of rubber seals. The cooling fan kept whirring nonstop, risking motor burnout over time. A slight vibration in the steering wheel was the engine mount rubber signaling fatigue. Dashboard warning lights flickering indicated unstable voltage. Gasoline fumes would seep into the cabin, leaving my hair smelling of fuel when I stepped out. Tires under prolonged one-sided pressure were prone to deformation, with wheel hubs getting hot enough to fry eggs. The windshield wiper motor also continuously drained the battery.
