Can an automatic transmission coast in D gear?
2 Answers
An automatic transmission can coast in D gear. In fact, for automatic transmission vehicles, coasting can only be done in D gear. Coasting in N gear may damage the transmission, and other gears are not suitable for coasting at all. When going downhill, it is recommended to use the restricted gears 2 or 1. Although the engine speed may be higher, fuel-injected vehicles do not supply fuel in this state, making it a fuel-saving condition. An automatic transmission generally refers to a car's automatic gear-shifting mechanism, where the control system of the automatic transmission selects the appropriate gear based on the engine speed and load during driving, replacing the driver's subjective judgment and gear-shifting operations. A typical automatic transmission car has six gear positions, from top to bottom: P, R, N, D, S, L.
Coasting in D gear with an automatic transmission is perfectly fine. I've been driving for decades and often do this, especially when going downhill by releasing the throttle—the car slows down smoothly and it's quite fuel-efficient. However, safety should be prioritized. For instance, during long descents, frequent braking can cause overheating, while shifting to neutral can be dangerous because the transmission in D gear still provides some engine braking, helping to keep the car under control. I recommend coasting only on short, flat stretches, such as easing off the throttle before traffic lights in urban areas—no issue there. Don’t forget to check your brake pads regularly and maintain your car to ensure everything works properly. I’ve grown accustomed to this method, finding it a good balance between fuel economy and driving safety.
