How long can a car be parked without turning off the engine?

[Dallas]

Leaving the car running continuously for several days is fine (provided there's enough fuel). Here are some related points: 1. Increased fuel consumption: If the engine remains on for over an hour while parked, fuel consumption will rise. Even though the car isn't moving, fuel is still being used. Although the RPM may stay below 1000, fuel consumption persists, typically increasing by 5%--10% depending on the vehicle. This explains why fuel consumption is higher in traffic jams compared to normal driving. 2. Idle protection: Forgetting to turn off the engine and idling for over an hour won't harm the car; modern vehicles are quite robust, and many now come equipped with idle protection features.

[DelCayden]

I often encounter situations where I need to temporarily park my car. The two biggest concerns when leaving the engine running are the rapid increase in fuel consumption and aggravated engine carbon buildup. One winter, I waited for 40 minutes with the engine on and the heater running while picking up my child, and the displayed fuel consumption soared to 3 liters per hour, equivalent to driving 20 kilometers. A mechanic mentioned that idling for over 30 minutes tends to make the air-fuel mixture too rich, doubling the rate of carbon deposits. Safety is even more critical—if exhaust fumes seep into the car in a semi-enclosed space like a parking lot, carbon monoxide can become fatal within minutes. During summer, when waiting with the air conditioning on, I usually limit it to under 20 minutes. If the wait is longer, it's safer to turn off the engine and step out of the car.

[StMichael]

It depends on the situation. When I was driving a taxi, I often left the engine idling with the AC on for half an hour. For regular family cars, it's recommended not to exceed 15 minutes. Idling not only consumes extra fuel but also causes lower engine temperatures, increasing wear and tear. I remember last year a friend idled for two hours to keep cool during a nap, which ended up killing the battery because the alternator couldn't fully recharge it. Legally speaking, extra caution is needed—big cities like Shenzhen have laws now where idling for over 3 minutes in public areas results in an immediate 200-yuan fine. Honestly, the safest bet is to turn off the engine as soon as you stop. If you really need to wait, it's better to spend a bit on fuel to move to a shaded spot—good for both the car and the people.

[OTravis]

Personal experience tells you: Never take shortcuts for convenience! Once, I left the engine idling in the garage while waiting for someone in winter. After just 25 minutes, I started feeling dizzy, only to later realize it was due to carbon monoxide poisoning. A repair shop test showed the exhaust concentration was 11 times above the safe limit. Now, I never idle for more than 10 minutes—it's literally playing with your life. In terms of fuel consumption, idling for an hour burns about 1.5 liters of gas, enough to drive over ten kilometers.

[Martinez]

This reminds me of my neighbor Lao Wang, who always likes to smoke in the car without turning off the engine. Last time, his battery suddenly died and left him stranded. The tow truck driver said idling only charges at one-third the efficiency of normal driving. Prolonged idling is most damaging to the engine piston rings and can easily degrade the engine oil. From a safety perspective, carbon monoxide levels in underground parking can exceed limits within just 5 minutes of idling, and there have been many tragic incidents reported in the news. My personal habit is to always turn off the engine if idling exceeds 5 minutes, and if I must run the AC, I leave a window slightly open to ensure ventilation.

[LauraMarie]

From a car maintenance perspective, let me share our fleet rule: never let the engine idle for more than 20 minutes. The reason is simple – prolonged low RPM operation reduces cooling system efficiency, potentially causing localized overheating, while the oil pump pressure becomes insufficient. Last year, one of our vehicles suffered cylinder scuffing due to this, costing over 8,000 yuan in major repairs. Nowadays during summer, I only start the engine and turn on AC when passengers are about to arrive – saves money and spares the vehicle. Oh, and remember to check the exhaust pipe position; idling becomes even riskier if it's blocked by snow.