I have met many drivers, most of them old-school, who believe that if you put the car in neutral, you save fuel. Those drivers truly believe that coasting in neutral saves fuel. This myth continues to live among drivers and it is being passed to younger drivers as well.
In this article I will explain why putting the car in neutral does not save fuel as some drivers think and why you should stop believing this.
The answer is no, putting the shifter in neutral does not save fuel. Many drivers continue to believe that if the car rolls with the transmission disconnected, with the clutch pedal pressed or on neutral, little fuel is consumed, but this is not the case because fuel continues to flow, as in normal driving. The engine revs are still up, which means that fuel is consumed.
What is the fuel consumption when the car is in neutral?
As mentioned above, the fuel consumption in neutral is not much different from the normal driving mode. Moreover, it may increase slightly if you drive in neutral, and not with the car engaged in gear with the gas pedal released. On average, on a long journey, you will get an increased consumption of about 0.2-0.5 liters per 100 km or 1176 to 470 miles per gallon.
Why putting the car in neutral does not save fuel?
The majority of drivers are thinking about saving fuel when driving. Needless to say, the logic is really visible here: the more rotations the engine crankshaft makes per unit of time, the more often fuel is sprayed by the injectors.
When the engine is idling, its speed is about 750-850 RPM, and when the car is moving, the engine speed is at about 2.000 to 3.000 RPM or even more. So, when we do a simple calculation here we would see three to five times fuel economy. That would be great, no? But in reality, it doesn’t work that way.
On old cars, the fuel was supplied to the engine differently than it is now, the mixture was prepared in a carburetor. This device with calibrated jets simply passed a certain amount of fuel and air through itself, depending on the operating mode of the engine. The fuel supply was always carried out.
Nevertheless, even on the advanced carburetor systems of later years of production, engineers implemented the ability to turn off the gas supply when coasting and forced idle economizers appeared.
For example, upon reaching 2.000 engine revs, the supply of gasoline when coasting through the idle system was completely shut off. So, the fuel did not go into the combustion chambers. But when driving in neutral, the fuel, of course, was supplied and, without this, the engine simply stalls.
In today’s engines, with injection systems, all cars have learned to effectively save fuel without any tweaks like putting the shifter in neutral. The system works incredibly simple: when the gas pedal is released and the crankshaft revolutions are higher than the specified ones, an electrical impulse is no longer supplied to the injectors and ignition coils.
No fuel is injected and the mixture in the cylinders does not ignite. Normal air is blown through the motor. As soon as the rpm drops below the boundary, the system starts the fuel supply, in the beginning with a lean mixture and bringing it to the standard for idling. In this case, the engine runs without load, its functioning is simply maintained.
Since the internal combustion engine can rotate the crankshaft while coasting, all vital systems like the alternator, oil pump, power steering, air conditioner compressor, vacuum brake booster, etc. remain operational. The auxiliary systems do not care what rotates the crankshaft what ignites the mixture in the cylinders or what energy comes from the wheels.
In practice, this leads to the fact that, when driving downhill in a gear, the fuel in the cylinders is not burned at all. When driving there with the car in neutral, the fuel will be consumed in idling mode. In the latter case, there is obviously no doubt of fuel economy.
Why driving with the car in neutral can be dangerous?
Another aspect that is important and many drivers don’t know about is that when driving with the car in neutral the braking distance will increase, especially driving with a disconnected transmission in a front-wheel-drive car.
Effective braking in an emergency situation is also possible only with simultaneous deceleration with the brakes and the engine because it will significantly reduce the braking distance.
Related to this aspect, those same drivers that think they will save fuel by putting the car in neutral also think that engine braking will wear the transmission and the engine.
This is not true, engine braking is a great thing to implement in your driving because not only does not wear the engine and the transmission, but it will help you in emergency situations, and it will also save fuel. When you drive down a slope with the shifter in one of the gears and with the foot off the gas pedal, especially in a manual car, the fuel consumption is almost 0.
This type of behavior is not only ineffective but also dangerous. Including position “N” at cars with automatic transmissions, you are effectively left without adequate control of your car. And in the event of an emergency or loss of control, it can cause problems.
In theory, putting the car in neutral should be as profitable as possible. There is no wheel engagement with the shaft, there is no torque, and the engine will consume less fuel. This method really gave results on an old carburetor engine, and not on a modern injection engine.
Today, engaging in the neutral gear, the car continues to maintain minimum revs. This is especially true for automatic transmissions. The internal combustion engine is configured so that in any case it will burn gasoline and give speed.
Thigs turn the opposite way when you drive the car in engaged gear and release the gas pedal. When driving like this, the engine completely shuts off the fuel supply, which does not happen in neutral. And this is considered an efficient and safe movement.