Your engine uses no fuel at all when you lift off, unless you slip it into neutral
There is a number on your own dashboard that settles this argument, and it takes two gestures to read it.
Set the trip computer to instantaneous consumption, get up to a steady 80 km/h in a high gear on a quiet road, and lift your foot cleanly off the accelerator without touching the clutch. The readout falls to zero and stays there while the car slows. Now press the clutch, or pull the lever back into neutral, and watch the same number climb back to something small but perfectly real. That is the entire question answered in about four seconds. A modern engine on a closed throttle is not sipping fuel carefully, it is being fed none at all, because the management system has stopped injection completely and is letting the wheels turn the engine over for free. Ask the same engine to sit in neutral and it has to keep itself alive, which costs roughly half a litre to a litre an hour depending on how big it is. The advice to knock the car into neutral and roll is older than the technology that made it wrong, and it survives because coasting feels frugal in a way that engine braking never has.
What a closed throttle actually tells the engine
The feature is called overrun fuel cut-off, and it is not an option or an eco gimmick. Virtually every petrol and diesel engine with electronic injection has it, which in practice means everything on European roads built since the early 1990s. The conditions are simple: the accelerator is fully released, the engine is warm, a gear is engaged so the wheels are driving the engine, and the revs are comfortably above idle, typically somewhere in the region of 1,200 to 1,500 rpm depending on the car. When all of that is true the injectors simply stop firing. Nothing is metered out, nothing is burned, and the trip computer is telling you the literal truth when it shows zero. As the speed drops and the revs fall back towards idle, fuelling is restored smoothly so the engine cannot stall, which is why the number reappears just before you come to a stop. What is happening mechanically is that the momentum you already paid for is being spent turning the engine over instead of being turned into heat in the brake discs, and the pumping losses inside that engine are what slow the car down. Engine braking is not the engine working. It is the engine being worked.
Neutral asks the engine to keep itself alive
Take the drive away, either by pressing the clutch or by selecting neutral, and the engine is on its own again. It has to produce enough power to overcome its own friction and drive the alternator, the water pump, the air conditioning compressor and everything else hanging off it, and that costs fuel. A warm mainstream petrol or diesel engine idles on somewhere between half a litre and a litre an hour, with a large engine or a cold one asking for more. Put a number on a single event and the honesty of the thing becomes obvious: a thirty second coast up to a roundabout at 0.7 litres an hour costs about six millilitres, which is not quite a cent. Nobody is being ruined by this. What matters is the direction rather than the size, because one option costs nothing at all and the other costs something every single time, and a driver in town meets a few thousand of those moments a year. Add them up and you get a litre or two annually, which is real but small. Anybody selling you neutral coasting as a serious economy measure is selling you the wrong end of the problem.
The one honest argument for neutral, and why the car does it better than you
Neutral does have a genuine physical point, and it deserves stating properly. An engine being turned over on a closed throttle soaks up a substantial amount of energy, so a car in gear slows noticeably while a car in neutral keeps rolling. If the road ahead is flat, the next junction is 400 metres away and you would otherwise have to feed in throttle again, rolling further really can mean using less fuel overall. Manufacturers agree with that logic, which is exactly why so many modern automatics and dual-clutch cars have a coasting or sailing function that opens the clutch the moment you lift off at a steady cruise, and why several go a step further and shut the engine down completely while the car is still moving, restarting it before you have any use for it. That version collects both prizes at once, free rolling and zero fuel, and it is safe because the car was engineered for it, with electric power steering and an electric vacuum pump keeping the controls fully alive. Your improvised version in neutral collects only the first prize and pays idle fuel for the privilege. And in the situation that comes up most often, where you were going to have to slow down anyway, neutral is simply the worse choice twice over: you buy fuel you did not need and then throw away the momentum through the brake pads.
What you hand over when you take it out of gear
The reason driving instructors across Europe object to coasting has very little to do with fuel. A car in neutral cannot be accelerated, and cannot be slowed by anything except its brakes, so both of your responses to a developing situation now start with an extra step. On a long descent that becomes a safety issue rather than an inconvenience, because brakes that are asked to hold the whole speed of a loaded car for kilometres get hot, and hot brakes fade exactly when you need them. Selecting a lower gear and letting the engine hold the speed costs nothing, saves the discs and gives you a car that responds the instant you ask. The British Highway Code warns against coasting in plain terms and most national driving schools teach the same, not because the fuel argument is close but because the control argument is not. Coasting with the engine switched off is a different and far worse idea again, prohibited outright in several European countries: the brake servo has two or three assisted pedal presses left in it and then the pedal goes hard, the steering can lock on an older car, and you have removed every system that was helping you. On an automatic, dropping into N while moving is not what N is for either, since it removes engine braking and, on some transmissions, interferes with the way the box is lubricated and cooled while the wheels are still turning it.
Electric and hybrid drivers are already doing the good version
In an electric car, lifting off does not cost zero, it pays. The motor becomes a generator, the deceleration you feel is energy being pushed back into the battery, and in stop-start traffic that recovery is worth a meaningful slice of range rather than a rounding error. Hybrids do the same thing with the engine shut off entirely, which is why a full hybrid looks so much better in town than it does on a motorway. Most electric cars also offer the other setting, a low or zero regeneration mode that lets the car sail almost freely, and that one is genuinely useful on an open road where the drag of strong regeneration costs more than it gives back. The habit that follows is the same one this whole article is about: look further ahead, lift earlier, and let the car harvest the speed instead of the brakes. One visible consequence is that friction brakes on an electric car barely get used, so pads can last extraordinarily long while discs sometimes suffer from the opposite problem and corrode from lack of work, which is why some models run a periodic cleaning cycle of their own. The wear does not disappear, it simply moves, and it mostly moves into the tyres.
The saving lives in the moment you lift off, not in the gearbox
Here is the part worth taking away, because it is worth roughly a hundred times more than the neutral question. What changes your fuel bill is not which position the lever is in, it is how far ahead you noticed. Spot a red light 300 metres out, lift off there and let the car come down on a closed throttle, and that entire 300 metres cost you nothing at all. Stay on the throttle, brake hard at 50 metres and you paid for speed and then converted it into heat, and you will arrive at the same red light at the same moment. The same applies to a queue on the motorway, to a roundabout you can already see is busy, and to a crest you know has a village behind it. Drivers who do this well use several percent less fuel than drivers who do not, in the same car, on the same road, which is a completely different order of magnitude from the six millilitres in the paragraphs above. It sits alongside the other levers that genuinely move the number: motorway speed, since drag climbs with the square of it, an empty roof box left on after the holiday, short cold trips, and a monthly tyre pressure check with a proper gauge, given that the warning light is an alarm rather than a gauge. If you want the full ranking of what is worth your attention at the pump, the fuel temperature myth is a good place to start.
What to actually do
None of this asks anything of you except leaving your hand alone and your eyes further up the road.
Stay in gear whenever you are slowing down. The fuel is already switched off, the brakes are spared and the drive is there the instant you want it.
Lift off earlier rather than braking later. Every metre covered on a closed throttle is free, and this is where the real saving is.
Prove it to yourself once. Instantaneous consumption on the display, high gear, foot off, and watch it read zero.
Leave the clutch alone until the revs are near idle or you actually need to stop or change gear.
Use the car's own coasting, sailing or eco mode if it has one. That system is allowed to do what you should not.
On a long descent, select a lower gear and let the engine hold the speed, using the brakes for corrections rather than for the whole hill.
Never switch the engine off while the car is moving. You lose brake assistance within a few pedal presses and gain nothing worth having.
In an electric car, treat lifting off as the recovery it is, and save the low regeneration setting for open roads where sailing suits the journey.
Frequently asked questions
Is it really zero, or is the display just rounding down?
It is really zero. This is not a display quirk but a documented control strategy, and anybody with a cheap diagnostic reader can watch the engine's own fuel rate and injector timing drop to nothing the moment the accelerator is released above the threshold. The reason it feels too good to be true is that we all learned to think of an engine as something that must be fed to keep turning, when in this state the wheels are doing the turning for it and combustion is not needed at all. The one thing to know is where the boundary sits: below roughly 1,200 to 1,500 rpm the management system starts feeding the engine again so it does not stall, so a long coast in too high a gear at very low revs is not the free ride that the same coast one gear lower would be. A cold engine also behaves differently, since the priority in the first minute or two is getting the catalyst up to temperature rather than saving anything.
Does engine braking wear out the engine, the clutch or the gearbox?
No, and the myth is worth killing properly. An engine on the overrun is under less stress than an engine pulling, because there is no combustion pressure on the pistons and bearings at all, while oil pressure and cooling carry on exactly as normal. Manufacturers design for it, which is why the strategy exists in the first place. The clutch is not being worn either, since wear comes from slipping a clutch rather than from having one fully engaged. The one way to do genuine harm is to force it, by dropping into a gear far too low for the speed, which over-revs the engine and can lock up the driven wheels for a moment on a slippery surface. Downshift in sequence, glance at the rev counter, and let the car settle between changes. On an automatic, the equivalent is using the manual gate or the paddles rather than fighting the box.
My automatic will not hold the speed downhill. What am I doing wrong?
Probably nothing, because most automatics left in D will happily upshift as the car gains speed on a gradient, which is the opposite of what you want. The fix is to take the choice away from the transmission: move the lever into the manual gate, use the paddles or the minus position, and select a gear low enough that the car settles at a speed you are comfortable with. Many cars also have a B or L position that does exactly this, and hybrids and electric cars use B for a stronger regeneration setting that works the same way from the driver's seat. Modern automatics with a good hill descent strategy will also hold a lower gear on their own once they notice you braking repeatedly, but on a long alpine descent it is better to choose the gear yourself at the top than to hope the software notices halfway down. Try the whole thing on a modest hill before you need it on a serious one.
What about the start-stop system? Is that the same thing?
It is the same idea applied at the other end of the journey. Overrun cut-off saves the fuel an engine would burn while you are still moving, and start-stop saves the fuel it would burn while you are not moving at all, which is the idle consumption described above, once you are stationary at a light. Both are aiming at the same waste. The systems are also designed to protect themselves, so a start-stop car will keep the engine running when the battery is low, when the cabin needs heating or cooling badly, or when the engine is not yet warm, and that is not a fault. Switching it off because the restarts annoy you is a legitimate preference, but be aware you are choosing to burn the fuel. What you should not do is try to imitate it manually by killing the engine at lights with the key, because the car is not set up for it and neither is the starter.
How much fuel does all of this save in a year?
Be honest about the two halves, because they are not remotely the same size. Choosing gear over neutral is worth a litre or two a year for a typical driver, which is a rounding error on a fuel budget and mostly matters because it is free and because the safety argument points the same way. Driving with your eyes further ahead, so that you lift off early and arrive at a smooth pace instead of accelerating towards obstacles you can already see, is worth several percent of everything you spend on fuel or electricity, and it also reduces brake wear and makes the car far more pleasant for anyone sitting in it. If you want a rough order of the levers available to you: motorway speed first, then anticipation, then tyre pressures, then removing whatever is bolted to the roof, then combining short cold trips into single journeys. The gear lever does not make that list at all.
