Is It Harmful to Rev the Engine in Neutral?

[OSteven]

Occasionally revving the engine in neutral is not harmful to the car. However, frequently doing so can cause some damage. When in neutral, the engine has no resistance limitation, which can lead to excessively high RPMs. The primary drawback of high RPMs is increased fuel consumption. Additionally, excessively high RPMs can cause abnormal wear and tear on the engine and place excessive load on the transmission gears, potentially leading to gear damage in severe cases. Although the gear is in neutral when revving, the transmission input shaft continues to rotate. During this time, except for the output shaft and the synchronizers of each gear, components like the input shaft and the engine are still rotating, resulting in uneven force distribution and uneven wear on various parts. Prolonged revving can also cause the engine temperature to rise, and the radiator's cooling efficiency will significantly decrease without the inflow of cool air.