Especially on long sloping down-hills one will be tempted to put the car in neutral and to let it coast, being propelled by its own kinetic energy. The idea is to reduce fuel consumption as the engine would not rev as high as when it is engaged. However, there are some issues to consider before you keep on rolling.
When coasting in neutral, the driver will not be able to quickly engage the engine and accelerate if needed. A situation could arise where it is crucial to gain speed to avoid a potentially harmful situation. Particularly situations requiring immediate response, such as traffic jams or other hazards can become dangerous very quickly.
By way of disengaging the engine, there will be loss of engine braking. Engine braking uses the engine's resistance to slow down the car. This is not possible when coasting in neutral. Consequently, it can lead to the brakes being used more often and with more force. This in turn can increase wear and potentially lead to brake fading, especially on long downhill slopes. Brake fading can lead to extremely dangerous situations. At German Motors, we typically ask about the driving behaviour of our customers in order to assess the wear and tear items and how to best manage them. Especially brakes can tell a lot about the way a car is being driven.
Modern engines are managed carefully through electronic control units. The idea that a car coasting in neutral uses less fuel may be a fallacy. Modern cars with fuel injection systems often have their fuel injectors shut off when coasting in gear (throttle closed, engine RPM above idle). Coasting in neutral actually forces the engine to continue running at idle, which can consume slightly more fuel.
While the idea is to reduce fuel consumption, saving some money, this practice can potentially increase tyre wear. The sudden engagement of the drivetrain when accelerating back into a gear puts extra stress on the tyres, potentially leading to premature wear.
In summary, coasting may seem to be a good way to reduce fuel consumption. At the same time, potentially dangerous situations can arise when the gearbox is not engaged. For safety purposes, German Motors will argue that it is best to avoid coasting, especially along long, winding slopes.
