Free wheeling in neutral

[luckystrike]

Does 'free wheeling' down hill in neutral do any damage to your car, or is it simply a good way to save on fuel?

[Hymie]

Although I now drive an automatic, in my manual driving days, when descending long hills I would slip the car into 5th gear with the engine revs often well below 1,000.

Many will no doubt argue that with the clutch depressed you have less control of the car – but I fail to see what extra control having the engine & drive wheels connected gives.

But the amount of fuel saved (between neutral and 5th gear) will be minimal and could result in more fuel consumed if the engine idle speed is greater than the 5th gear speed.

Your post reminds me of a colleague who switched the ignition off while coasting down hill to save fuel. As he turned into his drive-way, the steering-lock activated (by his turning of the steering wheel) and he crashed into a neighbours car.

[Graham-W]

It won't do any harm but it won't save you any fuel either. Modern cars turn off the fuel to the injectors whilst decelerating so you will use more fuel with the engine ticking over in neutral. You will also have less control of the car.

[sigma]

I used to have a Peugeot with a mileage computer that displayed fuel consumption. On a long hill in 5th gear and foot off the accelerator, it would show 999 mpg.

Switching off the engine going down hill you would loose power steering and probably brakes. The steering lock would only activate if you removed the ignition key

[TWR]

Not much fuel saving but increased brake pad wear.

[RAV1D]

How long is this hill descending downwards? must be a good few miles if your thinking of saving petrol!

[JonnyBoy12]

I have heard that this is illegal, but whatever you do, do NOT switch off the engine while coasting. If you do this then you may lose power steering, and also the brakes as well. May save a bit of fuel, but don't think it would be much. You could go a lot faster like this for no cost, so do not know what to advise you.

[MantaRay]

Coasting downhill will not do any harm to your car but it's not good practice. Firstly, it can leave you fumbling for a gear if you need power instantly and secondly it means extra wear and tear on the clutch and sychro's when going back into drive.
Early Saab's and Rover's had "proper" freewheel devices that worked brilliantly, you just backed off and had freewheel, the gear lever and clutch remained untouched...and your vehicle coasted [quite frequently in fact] and you saved fuel. On modern cars, as Graham-W points out, the fuel switches off on the over-run, but the engine braking is still robbing your car of it's inertia and trimming it's speed.

[Toureman]

To answer your question, it will not do any damage, it is a simple good way to save fuel.

There will not be any increased brake wear if you judge your speed correctly and put it back in gear if needed to slow it down.

It is not illegal.

[Graham-W]

Whist it may not be illegal the Highway Code advises against it.
Rule 122

Coasting. This term describes a vehicle travelling in neutral or with the clutch pressed down. It can reduce driver control because

engine braking is eliminated
vehicle speed downhill will increase quickly
increased use of the footbrake can reduce its effectiveness
steering response will be affected, particularly on bends and corners
it may be more difficult to select the appropriate gear when needed

[TWR]

I think you will find it is Illegal Tourman as you are not in full control of the car.

[Hymie]

So each time a driver depresses the clutch pedal, they are not in full control of the car – albeit only for a short while.

[TWR]

Did you read the Question that was put in by Lucky Hymie? It seems you have not.

[AlBags]

No damage ..
Won't save anything.

[Toureman]

I know it is not illegal TWR !

If you did lose control of the car and caused a crash then you could be prosecuted for careless or dangerous driving but it is not illegal !

[TWR]

Hi Tourman,with respect I'm not going into an argument over this, but you have limited control over the car with the gear disengaged, by doing what has been asked you do not have FULL control over the vehicle & this CAN cause if an emergency arose the driver crashing the car etc. no doubt some clever person will say check Google, Iv no need to.

[Toureman]

Completely agree with you TWR.

[MantaRay]

Going off subject here a little I know, but for those that consider coasting "not in full control of a vehicle" couldn't you argue the same point regarding the use of the cruise control which could potentially be more dangerous than letting a vehicle coast?

[vorta]

do NOT do this if your car has an automatic gearbox, they do not like the wheels being turned by coasting and the box in neutral, the back pressure created will damage the gearbox, i work for a bus company and if we are going to tow a bus (all have auto boxes) we have to remove a drive shaft to prevent damage. and as sigma says, you will get better fuel consumption if you coast in 5th with the clutch out (foot off pedal) as the engine will be driven by the road wheels and fueling will be reduced (999.9mpg as in my picasso diesel), with the clutch in the engine has to fuel itself to tick over so not as good as clutch out in 5th.

[whiskeryron]

It's possible to drive out of gear (free-wheeling) in a lot of situations. Your car is out of gear much of the time anyway (when stopped, between gear shifting), and this is just expanding the number of situations where you leave it in neutral. You can 'coast' between traffic signals and such that you expect to change. This will take all of the engine and transmission drag out of the picture. This is also safer (when used appropriately) in rainy conditions as it can prevent hydroplaning. There are many places in this world where you can leave the car in neutral for a up to a mile or so and maintain a safe speed.
Don't tailgate. Leave an adequate following distance. You will spend a lot less time braking/accelerating and overall wearing yourself and your car out reacting to those idiots in front of you.
Slow down and predict traffic signals. You can reach a speed that will get you stopped at the next signal, or still be rolling when it turns in your favor, and coast most of the distance. Most of the (normal) wear on clutches is in 1st gear from a stop, and if you can avoid stopping, you save fuel and mechanical wear and tear.
Even when 100% of the power appears to be coming from gravity on a downhill slope, most normal cars burn more fuel in a lower gear than in a higher gear, or idle. It seems to be related to keeping the engine at its normal operating temperature and/or making sure it instantly has power (doesn't hesitate) when you're ready to accelerate again.