driving in neutral to save fuel

Kilty_2

blue_haddock wrote: »

There is a technical name for what he is doing.

Scotch overdrive!

:rotfl::rotfl::rotfl::T:T

Pew_Pew_Pew_Lasers!

tsstss7 wrote: »

its illegal - hes not in full control of the car. I doubt it saves much cash either!!

No, it isn't illegal.

hothothot_3

thanks for the humerous and helpful replies, I will not be doing the same! - and will let him know before he causes a crash, although I suspect he been doing this for a long time.

SailorSam

The gears can help you slow down, if your brakes failed going downhill being in neutral could be fatal.

Wig

I would not do this in an automatic because it means you HAVE to put it in neutral and it could cause gearbox damage, which for automatics is very expensive, but on a manual you don't have to put it in neutral, you can leave it in gear, and put the clutch in.

Lots of people will say that all modern cars definately have fuel cut off in overrun - as they have in this thread and all the other similar threads. But not one of them will be able to prove that. On the otherhand I say that not all modern cars have fuel cut off in overrun, and I have been able to show some evidence in support of this.

This added to the fact that when you do dip the clutch your speed down hill is not slowed by the gearbox thus you travel further and faster down the hill whilst still retaining the ability to quickly lift your foot and apply engine breaking and brake pedal braking, making it perfectly safe AFAIC, means that I do this to save fuel when going down hill - in a manual car, wouldn't do it in an automatic.

Your friend would save fuel by switching to a manual car.

computershack

Wig wrote: »

Lots of people will say that all modern cars definately have fuel cut off in overrun - as they have in this thread and all the other similar threads. But not one of them will be able to prove that. On the otherhand I say that not all modern cars have fuel cut off in overrun, and I have been able to show some evidence in support of this.

Actually it has been taught as part of the City & Guilds for donkeys years. Its been said by the manufacturers ever since the introduction of the K-Jetronic Bosch system.

This added to the fact that when you do dip the clutch your speed down hill is not slowed by the gearbox thus you travel further and faster down the hill whilst still retaining the ability to quickly lift your foot and apply engine breaking and brake pedal braking, making it perfectly safe AFAIC, means that I do this to save fuel when going down hill - in a manual car, wouldn't do it in an automatic.

However you will prematurely wear the clutch thrust bearing which, on my Mondeo, is £480 in labour to change.

Your friend would save fuel by switching to a manual car.

More rubbish. If it was a certainty that automatics are more thirsty than manuals, then manual boxes would still be the norm for new HGVs whereas the reality is that they're now a special order for most lorry manufacturers.

Wig

computershack wrote: »

Actually it has been taught as part of the City & Guilds for donkeys years. Its been said by the manufacturers ever since the introduction of the K-Jetronic Bosch system.

Strange that those self same manufacturers, or at least one, Vauxhall, say in the car manuals that it is not an option fitted to all models.

However you will prematurely wear the clutch thrust bearing which, on my Mondeo, is £480 in labour to change.

Absolute rubbish, you should always replace the bearing at every clutch change and there's no chance (if it is always renewed) it will wear out by doing this or by keeping your clutch in at the lights for that matter. Plus I get a clutch changed for £100 labour. Obviously it varies on make/model which only goes to show further how silly your quote was, but my last 4 cars have been £100 or under for clutch. (edited, because I missed that you mentioned your Mondeo, Mondeos have crazy clutch repair prices).

More rubbish. If it was a certainty that automatics are more thirsty than manuals, then manual boxes would still be the norm for new HGVs whereas the reality is that they're now a special order for most lorry manufacturers.

I wasn't aware the OP's friend was driving an HGV.

kaya

computershack wrote: »

On overrun, i.e when going downhill and the engine isn't providing drive, if you leave it in gear the engine management cuts all fuel to the engine so it doesn't use any. By taking it out of gear, it is idling and therefore using more fuel.

BUT AS IT IS AN AUTOMATIC, putting it in neutral will completely shag the gearbox, blowing the valves and servos. If he looks in the owners manual, it'll say how to tow the vehicle and for an automatic with the driven wheels on the ground, that means a very short distance (usually around 1km) at usually under 10MPH. What he's doing is basically the equivalent of towing it at whatever speed he happens to be doing.

RUBBISH, with the engine TURNED OFF there is no transmission fluid circulating around the gearbox which will cause the failures you mention in your post, with the engine running the pumps still operate and the fluid still circulates so you can turn the drive wheels safely without causing damage, however if you put the car into neutral whilst moving you are coasting and not driving so you are not in control of the vehicle, very dangerous position to put yourself in

Hadrian

Pew_Pew_Pew_Lasers! wrote: »

No, it isn't illegal.

Correct, it was a wartime measure for buses. It was rescinded many moons ago. Also if you turn the engine off (As I once did!) the power steering packs up and it's almost impossible to turn the wheel.

kwaks

I have experienced this many times on a bike when it hits a false neutral. Trust me you have greatly reduced control when it happens.

Dipping the clutch (as suggested by someone) is a poor technique with potential consequences, what would you do if you had to release the clutch in an emergency yet your speed had increased due to the gradient? You run the risk of engine damage due to over revving, and very few cars have a slipper clutch, so say hello to your wheels potentially locking.

As said, this is a very poor technique, your friend is seriously misguided.