Does Shutting Off the Engine in Neutral Cause Damage?
3 Answers
Whether shutting off the engine in neutral causes damage depends on the situation: 1. For automatic transmission vehicles, the engine should be turned off in P (Park) gear; shutting off in neutral can cause damage. 2. For manual transmission vehicles, shutting off in neutral does not cause damage. The hazards of shutting off an automatic transmission vehicle in neutral include: 1. Excessive carbon buildup on engine valves and pistons; 2. Accelerated engine aging. Reasons for a manual transmission vehicle stalling in neutral include: 1. Idle speed being too low; 2. Excessive carbon deposits on the throttle body, idle control valve, intake valves, intake manifold, combustion chamber, spark plugs, and fuel injectors; 3. Fuel injector leakage.
I've thought about this quite a few times. Turning off the engine in neutral gear itself doesn't pose major issues for the car, as neutral gear is specifically designed to temporarily cut off power transmission. However, there are a few details to note: doing this frequently may accelerate carbon buildup in the engine because the sudden RPM drop before shutdown leads to incomplete fuel combustion. For vehicles with electronic power steering, the steering wheel becomes noticeably heavier after engine shutdown, which can panic inexperienced drivers. The most dangerous scenario is turning off the engine in neutral on a slope - if you forget to engage the parking brake, the car could roll downhill and give you a real scare. My standard practice is to come to a complete stop, hold the brake pedal, shift to neutral, firmly engage the parking brake, and then turn off the engine - this is the safest procedure that won't harm your vehicle.
Shifting to neutral before turning off the engine generally doesn't harm the transmission, but don't overlook other risks. When an automatic transmission vehicle stalls suddenly, the transmission gears are still rotating, and doing this frequently may accelerate wear. The battery also suffers - the ECU continues drawing power after stalling, which may make the next startup difficult. Once I did this in an underground garage and forgot to turn off the headlights, resulting in a dead battery the next morning that couldn't start the car. Parking on slopes is even riskier - I once forgot to engage the handbrake, causing the car to roll back half a meter and hit the curb. Now I've developed the habit of ensuring the gear is in Park or the handbrake is properly engaged before shutting off the engine.
