[TimG]

Have had several discussions lately with people debating whether it is more economical to take the car out of gear and coast where possible to save on fuel (for example approaching a roundabout or junction/ downhill) , or whether the car saves more fuel by simply lifting off the accelerator and leaving in gear?

Sure I read once that the fuel is shut off as soon as you remove your foot from the pedal so would therefore make no difference either way, just safer to have it in gear?

From a common sense view I thought that by leaving it in gear your revs are higher than idle = more fuel consumption but I could be wrong?!

Discuss

[minicabrio]

No need for a discussion, just a simple fact

Most modern engines cut the fuel supply in gear when there is zero throttle applied, and the engine is not labouring (i.e. when approaching a junction), thus during this time, no fuel is used.

If you are going downhill in a MINI, and lift off the throttle, you will be coasting for free

This only applies to vehicles with a manual gearbox

[super c00per]

Back 4 years ago when I was learning to drive I'm pretty sure I was told that this is illegal to do when driving in neutral...I May be wrong though!?!?!?

I have done this going down a very big hill once because the needle was past the last digit on the fuel gauge!!!!

[adams]

Fuel is certainly shut off, however the problem i have experienced with leaving it in gear is if the hill is not steep enough to be in gear with the throttle off then you will slow down too much. Also if the hill is really steep you would have to be in a high gear revving the bits off her to maintain the speed limit lol. However if you are coasting down the hill in neutral for a long way sat on the brakes, i cant imagine this is any good for your brakes lol . I probably have just quoted a load of waffle there so please correct my ignorance if im wrong people

[minicabrio]

Bascially, coasting is not a recommended activity - if you're car is out of gear you're not in complete control of the vehicle as you're unable to accelerate should the need arise.

If travelling downhill, I would recommend selecting as higher gear as possible (if travelling over 40mph, use 5th or 6th) and apply very gentle intermittant throttle to maintain speed. The economy under these conditions is amazing, and you remain in control of your vehicle.

[TimG]

So basically whether in gear or in neutral, as long as your foot is off the accelerator, either way no fuel is being used!

I guess that the fact that the revs are higher than idle if 'in gear' still doesn't mean more fuel is going in, the engine is simply being turned over by the movement thus not needing fuel?!

[minicabrio]

No, it does not cut the supply in neutral - the car must be in gear.

Engines running in neutral use fuel to keep a constant tick over - engines left in gear turn themselves over without the need for fuel.

All explained here:

Daily Fuel Economy Tip » Fuel Economy Tip - Coasting

[MarkW]

coasting is downright dangerous and means you are not in full control of the car, potentially causing a careless or dangerous driving offence.

when travelling downhill you should select a lower gear not higher and use engine breaking to control the car with assisstance from brakes. If you use a higher gear and control the speed using brakes you run the risk that on longer steeper hills you could overheat the brakes and ultimately be left with no means of stoping the car

[TimG]

Quote: Originally Posted by minicabrio (original)

No, it does not cut the supply in neutral - the car must be in gear.

Engines running in neutral use fuel to keep a constant tick over - engines left in gear turn themselves over without the need for fuel.

All explained here:

Daily Fuel Economy Tip » Fuel Economy Tip - Coasting

Cool, thats what I wanted to know!

[minicabrio]

Quote: Originally Posted by MarkW (original)

coasting is downright dangerous and means you are not in full control of the car, potentially causing a careless or dangerous driving offence.

when travelling downhill you should select a lower gear not higher and use engine breaking to control the car with assisstance from brakes. If you use a higher gear and control the speed using brakes you run the risk that on longer steeper hills you could overheat the brakes and ultimately be left with no means of stoping the car

Obviously I posted the above with a hope that people would factor in an element of common sense.

I'm not talking about steep gradients, but more like gentle downhill slopes on motorways.

Of course, don't try coasting down a steep hill

[MINI Poser]

If you have a trip computer on your car, put it on the average consumption option or whatever it is that shows the real time mpg, and you will see that when you have it in gear, but not actually pressing the accelerator, the trip reads 99.9mpg...

Or something...Im tired...

[Darthbladerni]

I never coast but i do just roll in gear when it needs to.

I had this argument on another Car Forum and it came to point everyone was agreeing that leaving it in gear is better than coasting.

[morrisminiminor]

Seems to me that there is a lot of nonsense being sprouted regarding coasting.
People will do whatever they can to save money on fuel especially as our greedy grasping government is taxing us to death. Our cloud cuckoo-land leaders are not affected as they swan around in cars paid for by the taxpayer but have awarded themselves a further 24K to soften the blow anyway.
1) If the engine management system cuts off the fuel supply, why does the engine keep running and the computer system register a very slight improvement in fuel consumption?
2) Why are you not in control if you are coasting? If you do need to get out of the way in a hurry, you would normally have to select a lower gear to accelerate more quickly. Additionally if you do coast you must pay much more attention to your driving environment and read the road much farther ahead.
3) If you do leave the car in gear with your foot off the accelerator, the revs are still 2000+ at 50MPH. This drops to idle speed while coasting. From that alone, you must be saving fuel.
4) Who passed the law outlawing coasting? Is it not the same idiots now testing the hard shoulder on motorways as the cost free method of improving traffic flow during the rush hour with no thought for vehicles which have broken down or quick response for our emergency vehicles? Makes perfect sense then!
5) An early claim was that had you to brake suddenly, the brakes in cars were not up to stopping the car on their own quickly enough. Nowadays even the cheapest car for sale has a braking system which far exceeds the recommendations listed in the highway code.
Finally, does anyone get more than 50MPG in their 1.6 petrol MINI? I did it during the fuel strike and got an average of 51.6MPG on a tank of petrol. Normally I get 43MPG

morrisminiminor

[WHITEY_]

But while traveling down a hill, what would you rather use? Brakes or your transmission? Just select a high gear that doesn't feel like its causing resistance (engine braking). It puts your transmission under a lot of stress - brakes are cheaper than transmission parts...

[ian67]

I would never dream of taking it out of gear,I only just back off the throttle if I want to up the mpg.

[jimmyt]

You should be accelerating down hill and use the extra momentum to propel yourself back up the other side

[mister.t]

I coast a lot round here I live right on top of a hill - I always coast in 4th or 5th and it does my fuel economy wonders!!

[Posts001]

I generally never coast, mostly cause I'm always in some sort of traffic

[MarkW]

Quote: Originally Posted by WHITEY_ (original)

But while traveling down a hill, what would you rather use? Brakes or your transmission? Just select a high gear that doesn't feel like its causing resistance (engine braking). It puts your transmission under a lot of stress - brakes are cheaper than transmission parts...

brakes may be cheaper than transmissions but I rather not risk overheating the brakes and not being able to stop when I need to.

why do you think theres a sign on most steep hills saying Keep In Low Gear ?

[Lawrothegreat]

With modern cars having ventilated disc brakes and high gear ratios (2nd gear = 60mph and so on) there is not such a need to engage low gears going down hill. Such actions only need to be reserved for driving large vehicles fully laiden down long hills.

I do not believe coasting in neutral is dangerous. Provided you do not switch the engine off, you have power assistance to the steering and brakes. This is only a hypothesis but could your braking performance be improved in neutral? - e.g. you are only braking against the momentum of the vehicle, not the momentum of the vehicle and the engine resistance.

The average car will not increase its speed much in one second of full throttle acceleration especially if you are cruising in a high gear. It takes much less than this to put the car into gear if you're in neutral.

Having said this, and despite doing it myself (I started a separate thread in the 2nd gen MCS forum), coasting in neutral is quite a drastic action to save fuel consumption. Though I employed it at the weekend and managed a reported 57mpg in a R56 MCS over 120 miles.