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This has been dealt with above.
The idling/fuel shut off falls in favour of idling in neutral because you can roll much further in neutral than in gear.
Wearing brakes out more quickly? No, you only coast when you WANT to maintain momentum and air + rolling resistance gradually scrib off speed. In fact, with the trend towards driving more slowly, a lot of people are having trouble with brakes by NOT using them sufficiently.
You would need to do an awful lot of braking to experience brake fade-which is the antithesis of fuel saving. Cooked brakes are like engine balance-motoring hacks prattle on about it when it has very little relevance to real world driving. A gullible public soak up the half truths.
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I know an elderly gent who used to drive coal lorries from a mine on a hilltop down to a town in the valley. In those days (1940's/1950's) HGV's were officially limited to 20mph and most would struggle to exceed 50mph on the level - he used to coast in neutral as it was faster than running in gear.
Not legal but meant more trips in a day.!
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You don't want to try that trick with a 2 speed axle or a pneumatic splitter though.
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I know an elderly gent who used to drive coal lorries from a mine on a hilltop down to a town in the valley. In those days (1940's/1950's) HGV's were officially limited to 20mph and most would struggle to exceed 50mph on the level - he used to coast in neutral as it was faster than running in gear.
Not legal but meant more trips in a day.!
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This makes me laugh, today i took a friend out to help her pick out a cheap car (we were successful by the way) and when i got to her house her younger sister was using one of those Theory test things on the PC, the driving test success thing with mock tests etc, all very good and everything. I was challenged to doing the test (got 50 out of 50 on the questions and 56 points out of possible 75 on the hazard perception, despite the fact you didnt have to do that test when i took mine, by the way) and one of the questions in it, actually two of them were revolved around coasting, about why you DEFINATLEY SHOULD NOT EVER DO THIS!!!
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UT:"I knew that would crop up-and it's wrong. Blame Jeremy Clarkson for promulgating that myth."
Not a myth - of course it all depends on the purpose of your coasting. If you are coasting towards a red light then you are better off doing it in gear with no fuel being used at all, as a bonus the unfuelled engine will save wear and tear on your brakes. If you're coasting down a hill but need to get back up the other side, the engine braking will rob you of kinetic energy, so you'd be better off in neutral, burning a bit of fuel idling the engine, but at the same time maintaining or increasing momentum. Depending on the situation both ways are the right way.
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Not a myth - of course it all depends on the purpose of your coasting. If you are coasting towards a red light then you are better off doing it in gear with no fuel being used at all, as a bonus the unfuelled engine will save wear and tear on your brakes. If you're coasting down a hill but need to get back up the other side, the engine braking will rob you of kinetic energy, so you'd be better off in neutral, burning a bit of fuel idling the engine, but at the same time maintaining or increasing momentum. Depending on the situation both ways are the right way.
When will people finally realise that coasting (or whatever else you want to call it) has no place on the public highway. OK, you may save a thimble full of fuel every full moon but in the meantime you have not been in full control of the car.
If you are so certain its a good idea book in for your driving test and drive like that, you would soon fail.
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I've done it for well over 30 years - never been close to having an accident because of it. Good drivers can anticipate situations. Modern drivers are told to use the brake to slow down, being in the "right" gear is given little consideration, what's safer - being in the right gear using engine braking or needlessly lighting up your brake lights every 10 seconds as so many modern drivers do?
When drivers are told how to drive the target audience is the lowest-common denominator.
Coasting is fine if you understand why you're doing it and what the road conditions around you are - more so with modern cars with anti-lock brakes, where as in the past I wouldn't coast in the wet to reduce the chance of locking the driven wheels during heavy braking.
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I've done it for well over 30 years - never been close to having an accident because of it. Good drivers can anticipate situations. Modern drivers are told to use the brake to slow down, being in the "right" gear is given little consideration, what's safer - being in the right gear using engine braking or needlessly lighting up your brake lights every 10 seconds as so many modern drivers do?
I've only been driving for about 4 years; my instructor recommended that I use engine braking and apply the gears correctly rather than rely on the brakes. I often find that (having asked why) it's drivers of automatics who obsessively brake in order to feel in control. Some don't even realise they're doing it.
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I've only been driving for about 4 years; my instructor recommended that I use engine braking and apply the gears correctly rather than rely on the brakes. I often find that (having asked why) it's drivers of automatics who obsessively brake in order to feel in control. Some don't even realise they're doing it.
There's a subtle difference, the highway code tell you to get the car into the highest gear as quickly as possible without labouring the engine, your instructer would have told you assess the road ahead and to ease off the throttle in good time rather than brake unnecesserily (all good advice) he would (should) not have told you to engine brake because this is not what the Highway Code states, in poor conditions it's possible to lock a wheel and lose control of the car through botched engine braking (which is why it's no longer taught). The correct gear to maintain the most control (via engine braking) is not the highest gear possible.
I almost exclusively drive automatics - I do not need to constantly "comfort brake" as I read the road ahead.
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Since you're determined to rerun the discussion, let's go.
What do you mean "not in full control of the car?"
Do you mean lack of engine braking or lack of available acceleration?
If your answer to either is "yes", then this precludes the use of high gears since acceleration and engine braking are feeble in tall gears.
Does the highway code tell you to drive around in low gears all day in case you might want to accelerate? No, it does not. It advises you to change up as early as possible.
What about proper automatics? Take your foot off the gas and the revs drop to little above idle. Add in torque converter slip and there's very little engine braking. Does the Highway Code advise against driving an automatic on safety grounds? No, it does not.
The "musn't coast" is a nice simple rule that is easily remembered by even the most intellectually feeble of drivers. The main risk of coasting is that a witless driver will forget that they are out of gear and when they attempt to accelerate, and become flustered when the engine screams and the car doesn't pull forward. But this a problem with the driver, not the technique.
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Coasting works every time, I've been doing it for years (before servo brakes came along, with the engine off completely- restarting it using the clutch) the car travels much further in neutral than in a gear and if you're approaching a junction that you have to stop at anyway so you might as well use the car's weight and momentum for free.
On Madeira you can coast for over 3km - but only downhill :)
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Coasting works every time, I've been doing it for years (before servo brakes came along, with the engine off completely- restarting it using the clutch) the car travels much further in neutral than in a gear and if you're approaching a junction that you have to stop at anyway so you might as well use the car's weight and momentum for free.
On Madeira you can coast for over 3km - but only downhill :)
For feks sake stay on Madeira.
What you are doing is totally stupid and dangerous.
For starters the fuel you save will be less than brake wear.
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Coasting works every time, I've been doing it for years (before servo brakes came along, with the engine off completely- restarting it using the clutch) the car travels much further in neutral than in a gear and if you're approaching a junction that you have to stop at anyway so you might as well use the car's weight and momentum for free.
On Madeira you can coast for over 3km - but only downhill :)
For feks sake stay on Madeira.
What you are doing is totally stupid and dangerous.
For starters the fuel you save will be less than brake wear.
Strange that old Rovers and Saabs with a freewheel built into the transmisson still pass MOTs if coasting is so dangerous (they didn't have servo brakes so irrelevant whether engine was running or not.)
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Link to Honest John answer about coasting. Suppose he does not have a clue.
http://www.honestjohn.co.uk/askhj/answer/34186/fuel-economy-when-coasting
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Unfortunately his answer isn't right. While an engine uses no fuel whilst in overrun, it is being kept spinning by the loss of vehicle momentum thus requiring morem frequent accelerations leading to a net increase in consumption.
I don't know why this issue exercises you so much. If you don't like it, don't do it.
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Unfortunately his answer isn't right. While an engine uses no fuel whilst in overrun, it is being kept spinning by the loss of vehicle momentum thus requiring morem frequent accelerations leading to a net increase in consumption.
I don't know why this issue exercises you so much. If you don't like it, don't do it.
So only myself and Honest John think that coasting does not save fuel, OK by me, never felt safe in crowds.
I don't like it and I don't do it but it does worry me that many people on here think its OK when it is possibly illegal and definitely bad practice.
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So only myself and Honest John think that coasting does not save fuel, OK by me, never felt safe in crowds
Your instantaneous fuel consumption figure is totally irrelevant.
1.) Overrun comes at the expense of lost momentum.
2.) Lost momentum is deferred fuel consumption.
It's a simple fact that it takes more horsepower to spin the engine at a higher RPM than it does at a lower RPM. There is no discussion to be had.
Generally speaking, you will get the best fuel economy by covering your journey with the fewest total number of engine revolutions.
This is why car makers use tall gears.
This is why bicycles come with freewheels, with the the exception of bumptious nerds who push 'fixies' round waitrose. :)
The exception is when you have to lose momentum anyway-say because you are approaching a junction. In this case, engine braking is preferable because the engine braking warms the oil.
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s the fuel you save will be less than brake wear.
Strange that old Rovers and Saabs with a freewheel built into the transmisson still pass MOTs if coasting is so dangerous (they didn't have servo brakes so irrelevant whether engine was running or not.)
I owned and drove two old Rovers with freewheels.: a 1946 16 and a 1953 75.
Only a complete numpty would use Freewheel going downhill in the 16 as the rod drum brakes faded badly on long descents and produced clouds of very hot smoke. (which smelt horrible). And of course, teh car would not stop... which produced a few intersting moments. Even under engine braking with the freewheel disengaged, the brakes would overheat.
The Rover 75 had better hydraulic drum brakes but again only a numpty etc...
Of course they pass an MOT as the MOT only tests brake efficiency.. and not freewheels etc..so the above comment about MOTs is a total irrelevance. Just eneter it for the MOT with the Freewheel in OFF position.
I never had any MOT problems with brakes.. (the 16 steering was another story)
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"Coasting means you're not in full control of the vehicle." Er, HELLO Mr 1950s man!
I'd like to try it on the near 5 mile descent from the Hindhead tunnel going north. I have a 3-figure fuel consumption thingy, so should spend several minutes at 999 mpg.
Cruise control of course maximises consumption by keeping speed uo going uphill and down going downhill. Doh! Us humans ought to be able to adjust speed slightly up and down hill to get the best figures.
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Would anyone on here who is so pro "coasting" be prepared to suggest to a family member that they should practice "coasting" during their driving test?
Would anyone on here who is so pro "coasting" be prepared to standup in court after being charged by the police for dangerous driving after an RTA and argue that "coasting had nothing to do with the accident and was perfectly safe?
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Ignoring the economy argument (and the difference is probably minimal), coasting out of gear means you are out of control.
Hence on roads with steep downhill sections is says "Keep in a Low Gear" and does not say " Feel Free to Coast". Out of gear there is no engine braking and no ability to immediately accelerate if necessary. Engine braking is far preferrable to using the brakes as there is no waste of brake pad linings which are more expensive than fuel.
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Ignoring the economy argument (and the difference is probably minimal), coasting out of gear means you are out of control.
If it is so minimal, why do you think engine designers use such steep gearing? At 20mph it takes more horsepower to turn the engine than it does to move the car down the road.
Define 'out of control'. What is the difference between being in top gear at 1000 RPM and in neutral at 900? Nothing, other than the fact that you have selected a gate and, psycologically, you feel 'in control'. There's b***** all engine braking and available acceleration.
Hence on roads with steep downhill sections is says "Keep in a Low Gear"
That's aimed at 44 tonne trucks that do have problems with overheating brakes. Your car does not.
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To add weight to your argument here, as the Prius got a mention earlier in the conversation, that has effectively got freewheel built in too.
It's a "CVT" in that it has an effectively infinite set of ratios, but not a CVT in the conventional sense, as the gearing is direct (so no losses). Matching of engine speed to wheels is done by varying the load on the sun gear of its epicylic transmission, altering the ratio of planet carrier (engine) to annulus (final drive). Electric drive is direct to the annulus as 'leccy motors are rather less worried about revolutions.
However, there's another effect downhill or while decelerating gently. If you get the throttle in the right place, there's no load. The engine stops as no power is required. No drive is required, so no power is fed to the electric drive motor. No deceleration is being asked for so there is no load applied by the annulus motor/generator and as the engine is stopped there's nothing being scavenged by the sun gear motor/generator.
The transmission is turning idly and......you are freewheeling. Nothing is acting on the vehicle bar gravity and wind resistance / other frictional losses. Yup, that Toyota HSG system effectively has a freewheel system that you cannot turn off.
Funnily enough, it doesn't suddenly become dangerous when it does it. As I cannot see why a competant driver who knows what he or she is doing should be any more dangerous in this situation than a computer made by Toyota, I am forced to the inescapable conclusion that the naysaying on "safety" grounds is unfounded.
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Engine braking is far preferrable to using the brakes as there is no waste of brake pad linings which are more expensive than fuel.
If you don't use the brakes sufficiently, the corrosion will eat them and the pads faster than you would if you used them hard. When you hear of brake discs on the back axle needing replacement after 30,000 miles you don't think it is excessive use that wears them out, do you?!
Charged with dangerous driving due to being in neutral?
Grow up. No one has ever been charged with dangerous driving for being in neutral.
If engine braking is so important then automatic transmission users should end up in court charged with dangerous driving. They don't.
Motorcyclists often clutch-in as they brake. Should they end up in court too?
What rot!
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Motorcyclists often clutch-in as they brake. Should they end up in court too?
You're supposed to - I have only had a few bike lessons (had to give it up as I ran out of money....) and it was a recommended thing to do because of the sequential gears. You can't say they're doing anything dangerous; it'd be more dangerous to get stuck in the wrong gear and be unable to move off properly....
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If engine braking is so important then automatic transmission users should end up in court charged with dangerous driving. They don't.
Welcome to reality. Some autos provide engine braking when travelling downhill, at least my nine-year old Saab does. Presumably it's not unique? Or has auto transmission technology regressed in the intervening years?
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The typical engine braking from a traditional torque convertor automatic in high gear is pretty feeble. Fpr a start they tend to be geared higher than manuals. Plus, they often unlock the torque convertor at low engine speeds.
Are you not in control of your bicycle if you don't keep continuosly pedal?!
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Engine braking?
What out of date thinking that is. Using the engine to brake the car to save 'wear' on the brake pads dates from the time brakes were so unreliable that they couldn't be trusted to work on downhill streches (whether on Madeira or not). As for the argument that the brakes cost more than the fuel does, so does the clutch, pistons, crank, valve etc al of which work harder when forced to slow the car instead of speed it up.
Do you also blip the throttle before switching off to put fuel into the chambers - a common practice 40 years ago!
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Nice to see this debate resurrected, although a recent contributor or two clearly does not have the requisite basic knowledge of physics....see my post far above!
Well said 'unthrottled', you are absolutely correct in all your responses. There are also good responses to the twaddle about 'not being in full control of the car'. This might possibly apply on long mountain descents where one can switch the engine off completely, making sure you don't engage the steering lock. You need to know your car as to when the vacuum brake servo runs out necessitating much extra pressure on the brake pedal.
No doubt this admission will result in disapproving replies!
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If modern braking systems can't stop a car with the engine drive disenagaged when coasting, the entire MOT system for brake testing is wrong.
The "don't coast in neutral" story was going when I was born and cars had rod or cable (eek!) brakes and servos and vented disk brakes were unknown - so over half a century ago. Technology has changed a lot...hand signals anyone?.
Of course there are drivers who - if they were coasting in neutral - would forget and rev and rev with no results - or blow up their engine . For comparison there are drivers who drive and don't look at the road but text and adjust their stereoes at teh same time so the lady in a bungalow 50 metres away can hear what they are playing behind her double glazing......
Far more important driving issues to worry about..
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The "don't coast in neutral" story was going when I was born and cars had rod or cable (eek!) brakes and servos and vented disk brakes were unknown - so over half a century ago
There was also no or iffy synchromesh, so it was more difficult to get back into gear and then double declutch your way down the ratios for max engine braking [younger readers will have no idea about doing this....memories of brake failure from a pre-MoT rusted brake pipe on a downhill stretch in the Yorkshire dales!
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There was also no or iffy synchromesh, so it was more difficult to get back into gear and then double declutch your way down the ratios for max engine braking [younger readers will have no idea about doing this....memories of brake failure from a pre-MoT rusted brake pipe on a downhill stretch in the Yorkshire dales!
ah the joys of double declutching!
At least on Rovers with Freewheel , you did not neeed the clutch to change gear.. just foot off accelerator.. but as you had noo engine braking no use on downgrades..
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I understand what they're on about, these nutters in the government Department of Transport, or whatever.
The Law is an Ass. The Highway Code is wrong.
By 'loss of control' they are referring to the loss of control you would experience by turning the ignition key off, and the steering lock coming on. Then you do, truly, lose control. Don't ever try this in the interests of curiosity, as the steering lock will grab more, the more you try to steer the car.
Anyway, the official guidance is wrong, outdated, and just plain daft. Sack them all.
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I'm not on any tablets! But it does me a world of good to observe that my prose works as a medicine. Not sure for which parts though.
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Although I'm not in the habit of coasting myself, apart from rolling slowly in downhill traffic queues, I can't see it's particularly dangerous in modern cars as long as you keep an eye on the speed. After all, automatic cars more or less coast on the over-run, providing very little engine braking.
But turning off the engine while coasting is a no-no. Like someone said, it could activate the steering lock depending on how far you turn the key - but also the power assistance the steering will stop and the assistance to the brakes will disappear after a couple of applications.
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