Does coasting in neutral harm an automatic transmission car?
2 Answers
Coasting in neutral can harm an automatic transmission car. When the car is coasting in neutral, the engine idles, and the transmission oil pump rotates at a lower speed, resulting in lower oil pressure. Meanwhile, the output shaft of the transmission rotates at high speed driven by the wheels, which causes the gears and friction plates inside the transmission to rotate rapidly, generating significant heat. If the oil pump pressure is low and the transmission oil circulates slowly, the heat cannot dissipate in time, leading to high internal temperatures that may damage the transmission. The more serious issue with coasting in neutral is safety. When coasting downhill, the car moves forward due to inertia and gravity. If the car is in gear, the engine is "dragged" by the wheels, providing a braking effect.
As an ordinary driver with decades of experience, I truly believe coasting in neutral with an automatic transmission is quite harmful to the car. While many claim it saves fuel costs, in actual driving, I've found it leads to insufficient transmission lubrication because the oil pump rotates too slowly in neutral, resulting in inadequate oil pressure. Over time, this can cause the gearbox to overheat or wear out faster. I learned this the hard way—when helping a friend with their car, frequent coasting led to repairs costing thousands, which wasn't worth it. Safety is also compromised: coasting in neutral reduces engine braking assistance, making it easier to lose control on downhill slopes. Honestly, modern cars are designed with fuel-saving systems in Drive (D), making coasting unnecessary. Safe driving is far more important than saving a little fuel.
