Does Coasting in Neutral Save Fuel in Manual Transmission Cars?
2 Answers
Coasting in neutral with a manual transmission does not save fuel. Here are the reasons why coasting in neutral does not save fuel: 1. The carburetor operates based on the amount of air intake. Regardless of the gear, as long as the car is coasting in gear, air is involved. The higher the gear, the greater the air intake, leading to increased fuel consumption. In contrast, when coasting in neutral, the engine defaults to idle speed, so coasting in neutral does not save fuel. 2. When coasting in gear, the throttle is released, reducing the engine's load, and the vehicle is in a state of engine braking. At this point, the fuel injection system automatically cuts off fuel supply. However, when coasting in neutral, the engine control unit (ECU) defaults to idle speed and continues to inject fuel to maintain it. Therefore, at least for now, coasting in neutral does not save fuel but instead consumes more.
I used to think coasting in neutral with a manual transmission saved fuel, having driven older cars where I believed leaving it in gear would slow the car down. Later, I realized this idea is outdated—modern fuel-injected cars actually save more fuel when coasting in gear because the engine control system automatically cuts off fuel supply during deceleration, consuming no fuel at all. In neutral, the engine still idles, wasting fuel for no reason. After testing different models, I found that while short distances show little difference, coasting in gear on long downhill slopes can save nearly 10% on fuel costs, plus it offers better control. Moreover, coasting in neutral is dangerous—losing engine braking and relying solely on brake discs to slow down increases risks of brake failure or skidding on slippery roads. I recommend practicing anticipatory driving: downshift early and avoid pressing the accelerator, saving fuel while staying safe.