Is It Harmful to Park in P Gear Without Turning Off the Engine While Waiting?

[DelNaomi]

Parking in P gear without turning off the engine is harmful. Here are some details about parking in P gear: 1. Hazards: Although the car can be turned off without shifting to P gear, doing so may damage the transmission and engine. It is recommended to shift to P gear before turning off the engine. The P gear mechanically locks the output shaft of the transmission to secure the vehicle, preventing it from moving. 2. Correct Procedure: The most suitable parking sequence for the vehicle is to first stop the car on a level surface, then shift from D gear to N gear, engage the P gear, and finally pull up the handbrake to complete parking before turning off the engine.

[Darlene]

I often encountered similar cases when I ran an auto repair shop. Keeping the car in P gear without turning off the engine for a long time indeed poses risks. When the engine idles, the cylinder temperature remains low, leading to incomplete fuel combustion which easily causes carbon buildup—especially noticeable in today's direct-injection engines. The worst case I've seen was a car that idled daily for three months outside a shopping mall while waiting, with carbon deposits on the throttle body so thick you could scrape off chunks. Additionally, running the AC for extended periods keeps the compressor working continuously, causing extra wear on belts and bearings. Not to mention idling with the AC on in hot weather—the cooling fan runs nonstop, draining the battery extremely fast. Once, during a customer rescue, I found his battery completely dead after idling for two hours while waiting for his child's tutoring session. My advice: turn off the engine if idling exceeds 10 minutes, and avoid running the AC for more than half an hour if necessary.

[DelBrooke]

This issue really resonates with me. Last week while picking up my wife from work, I left the car idling in P mode with AC on for half an hour outside her hospital. The next morning, the engine started with noticeable vibrations, and black soot came out of the exhaust pipe. A mechanic friend diagnosed it as catalytic converter poisoning caused by prolonged idling. He explained that during cold engine operation, exhaust contains high levels of unburned hydrocarbons that directly coat the converter's honeycomb structure. Now each repair bill costs as much as six months' worth of coffee. Recent research also revealed that prolonged AC use while parked risks carbon monoxide leakage into the cabin, especially dangerous in underground parking. Our community had a news story last year about a car owner who nearly had an accident while sleeping in an underground garage with AC running. Now I always carry a book for temporary stops - turning off the engine and reading with windows open saves fuel and ensures safety.

[DiAurora]

As an environmental monitoring officer, I must say this habit has a significant impact. Test data shows that idling for one hour in an ordinary family car emits PM2.5 equivalent to driving 30 kilometers under normal conditions. When in P gear, the transmission oil pump doesn't operate, causing slow oil circulation and localized overheating—a colleague's CVT transmission required major repairs due to this. Another easily overlooked point: idling at night with headlights on for prolonged periods can continuously discharge the battery, potentially damaging the plates. During our last vehicle inspection, we found that official cars frequently left idling had batteries with lifespans shortened by half a year on average. My advice is to turn off the engine if idling exceeds five minutes. If you must run the AC, switch to recirculation mode to reduce carbon buildup. Carrying a portable charging fan is far more cost-effective than keeping the AC running.

[DeEmma]

One winter night, I picked up my girlfriend from work and waited for half an hour with the car in Park mode and the heater on. The next day, the engine warning light on the dashboard came on. The repair shop read the fault code, which indicated an abnormal oxygen sensor. The technician said that the exhaust temperature was too low during idling, and the sensor was contaminated by unburned gasoline. The mechanic wiped the parts while explaining that cars with start-stop functionality are better off, as regular cars are prone to issues if idling exceeds twenty minutes. This is especially true when the air conditioning compressor is running, as it increases engine load but provides insufficient cooling. Last time, a neighbor’s Tiguan had to spend over 3,000 yuan on turbo cooling system repairs due to long-term idling with the AC on. Now, I’ve developed the habit of carrying a thermos when going out—drinking hot water in winter is more comfortable than using the heater.

[MartinRose]

I used to take long-distance drives and often rested in service areas with the gear in P mode. Once, I even slept for two hours with the air conditioning on. Later, I noticed an inexplicable increase in fuel consumption, and upon inspection, found that the throttle body was clogged with carbon deposits. The mechanic pointed at the carbon buildup and explained that at idle, the throttle opening is minimal, and the rich air-fuel mixture is particularly prone to coking. What's worse, the electric fan kept running, and all the willow catkins and fluff clogged the condenser. Last summer, my car's AC stopped cooling, and when we opened it up, the condenser looked like it was covered with a blanket. Now, especially for cars over five years old, it's crucial to pay attention—rubber hoses exposed to prolonged heat are prone to aging and leaks. It's recommended to bring a folding chair and wait outside the car. If you must rest inside, don't exceed twenty minutes, and always leave a window slightly open for ventilation.