Does Revving the Engine in Neutral Gear Harm the Engine?
3 Answers
Revving the engine in neutral gear can harm the engine. The neutral gear is equivalent to the neutral position in a manual transmission. When this gear is engaged, the engine's power output is disconnected from the vehicle's traction system. Automatic transmissions should not be coasted in neutral, as it can damage the transmission fluid and does not save fuel. When parking on a slope, always fully depress the brake before shifting into neutral and engage the handbrake if necessary to prevent the vehicle from rolling backward. Tips for using automatic transmission gears: 1. P (Park) gear: After shifting into this gear, the transmission is locked, preventing the vehicle from moving. Starting the car is possible in this gear while pressing the brake. 2. R (Reverse) gear: Used for reversing. Ensure the car is completely stopped before shifting into this gear to avoid damage. 3. D (Drive) gear: The forward driving gear, used for most road conditions except when climbing steep hills or descending long slopes. 4. L (Low) gear: Primarily used for climbing steep hills or descending long slopes to control speed and avoid prolonged brake use, which can lead to brake failure.
I saw people discussing online whether revving the engine in neutral gear harms the car. I think this needs to be explained from the principles of engine operation. When revving the engine in neutral, the engine operates at high RPMs without load, and the combustion chamber pressure does spike suddenly. Although modern engines have rev limiters to prevent over-revving beyond the fuel cutoff zone, running at 6,000-7,000 RPM puts much greater stress on piston rings and crankshaft bearings than normal operation. Doing this for extended periods is particularly damaging—oil film can break down, leading to metal-on-metal friction. However, briefly revving the engine for a few seconds (under 10 seconds) isn’t a big issue, as the engine temperature won’t have time to skyrocket. The key is how you rev it. If you recklessly floor it during a cold start before the oil has properly circulated, you’re essentially paying to hear noise—you’ll regret it when the repair bill comes.
That day at the repair shop, I was chatting with the mechanic about this, and he said that revving the engine in neutral is actually most damaging to the transmission oil pump. Even though the gear isn't engaged, the torque converter is still spinning, and suddenly increasing the RPM can cause the transmission oil temperature to spike instantly. I've personally seen a Camry that frequently revved its engine, and its torque converter lock-up plate was completely worn out by 50,000 kilometers. However, as for the engine itself, doing it occasionally doesn't have much impact, as the ECU speed limiter keeps it in check. What really damages the engine are those older cars, especially carburetor-era vehicles without RPM protection, which are prone to cylinder scoring. Modern cars have knock sensors to protect them, so a few quick revs can be considered as cleaning carbon deposits, but doing it frequently will definitely shorten the engine's lifespan.
