[AjayJoshuaN]

Originally Posted by a4anurag

In this I have attached three consecutive shots to show the deceleration (Notice the RPM dropping) but the fuel flow is '0'). Engine load too is 0.

Really appreciate your effort in getting these results

The point proved here is that fuel is not consumed during the period of coasting in gear.

But many people seem to be confused.

They are thinking that coasting in gear saves more fuel than coasting in neutral. If this point needs to be verified, the distance traveled by the vehicle also needs to be taken into consideration:



Because engine braking will destroy the useful momentum gained by burning fuel, -> which will decrease the distance traveled by the vehicle during coasting in gear, -> which in turn would need additional fuel to be burnt to regain the same distance traveled by coasting in neutral.

[Joe-Ker]

nice work to gather the data. but one more metric would be required to make this an aplles to aplles comparison. that is the acceleration figures. or rather the deceleration.

we have established that the fuelling is indeed zero or negligible when coasting. but what about the distance travelled? wouldnt the engine be braking the car while coasting in gear?and you have to accelerate again to regain lost momentum. but in case of coasting in neutral it travels much more distance as there is no engine braking. so coasting in neutral does save fuel if you consider a trip per se..

especially highways (level or small inclines)..accelerate to 100..coast to 85 in neutral. then again. accelerate..to 100 (this ia what many of you have seen drivers do).
If you accelerate tho 100 then coast in gear to 85 then accelerate back to 100 u will have to spend lot more time accelerating than in previous case because engine is braking when you lift off.

if you want to coast to a stop and want engine braking in an mpfi car then costing in gear gives better FE

so there are scenarios where coasting in gear does save fuel and some where you dont.

a note of caution: coasting in neutral reduces drastically the drivers ability to control the vehicle in an emergency. so if you are not an expert driver you may not be able to judge if it is safe to do it or not. experience after all is the best teacher!

[AjayJoshuaN]

Originally Posted by sgiitk

Try this in the UK and if you are giving a driving test you FAIL.

Volkswagen CC uses the concept of coasting. So if the driving test is done with a Volkswagen CC, will using this car give the test a fail? What do you think?

Please check:

http://www.autocar.co.uk/blogs/green...t-through-life

http://en.volkswagen.com/en/innovati...ffunktion.html

[sgiitk]

Originally Posted by AjayJoshuaN

Volkswagen CC uses the concept of coasting. So if the driving test is done with a Volkswagen CC, will using this car give the test a fail? What do you think?

Please check:

http://www.autocar.co.uk/blogs/green...t-through-life

http://en.volkswagen.com/en/innovati...ffunktion.html

I guess they will ask you to disable the coast feature. I wrote this to highlight the basic - never coast in neutral. Coasting with the gear connected is fine.

[youknowitbetter]

Hi all - taking a cue from an old saying 'necessity is the mother of invention', rising fuel prices and the mentality of extracting more per liter, I started reading up on coasting and I thought why not get the feedback of fellow members of this group. I have 2 fairly small petrol cars - Tiago and Seltos. MID shows 12.5 and 10.2 respectively for both cars and I have been trying to drive these 2 cars in different driving styles to see if there is any change in the mileage. Coasting did help in boosting Seltos' mileage but hasn't resulted much difference in Tiago, which I am finding bit strange as earlier I used to get 14/15ish as my mileage (quoting solely based on MID and have not independently verified and I understand that there could be +/- 10-15% difference vis-a-vis the MID figures). Would love to know the thoughts of fellow members to understand what is being done by them and how to improve the fuel efficiency. Thanks

[AjayJoshuaN]

When I travel from Chennai to Trivandrum, I usually reach 100km/h and coast in neutral to 80 km/h and repeat this. Sometimes I would reach to 110km/h or 120 km/h and coast in neutral to 100 km/h as needed and repeat this.

The AFE shows 20Km/L on my Xylo.
I never need to stop on the way anywhere for refuelling when I coast in neutral.

What I realised is that in order for the coasting in neutral to work effectively in saving fuel,
1. the style of driving will need to change in such a way as to reduce pressing the brake or use engine braking to slow down the car. Because everytime the brake is pressed, fuel is lost. Everytime engine braking is used, fuel is lost, due to the destruction of useful momentum.
2. Cold tyre pressure should be maintained correctly, preferably +2 psi above recommend pressure, accounting for gauge errors
3. Determine the speed at which you feel more wind resistance slowing down the vehicle, and avoid going too much above that speed. Usually I feel more wind resistance kicking in at speeds above 85 ~ 90 km/h, so I maintain speeds around 80 ~ 100 km/h on the highway.

On usual roads filled with traffic, it is totally a different scenario, because braking will reduce the effectiveness of coasting in neutral.

[srvm]

Originally Posted by AjayJoshuaN

When I travel from Chennai to Trivandrum, I usually reach 100km/h and coast in neutral to 80 km/h and repeat this. Sometimes I would reach to 110km/h or 120 km/h and coast in neutral to 100 km/h as needed and repeat this.
.....
In usual roads filled with traffic, it is totally a different scenario, because braking will reduce the effectiveness of coasting in neutral.

Please dont coast in neutral. It is plain wrong and in some countries illegal as well since you cannot accelerate immediately if the need arises. If anything, coast in (highest) gear which is safer as well as more fuel efficient than coasting in neutral. (Lots of reading material available in the internet on why it's more fuel efficient than coasting in neutral)

[AjayJoshuaN]

Originally Posted by srvm

Please dont coast in neutral. It is plain wrong and in some countries illegal as well since you cannot accelerate immediately if the need arises. If anything, coast in (highest) gear which is safer as well as more fuel efficient than coasting in neutral. (Lots of reading material available in the internet on why it's more fuel efficient than coasting in neutral)

Please read the previous posts in this thread, most of these points have already been discussed.

[fordday]

Originally Posted by AjayJoshuaN

Please read the previous posts in this thread, most of these points have already been discussed.

Sir, not coasting in neutral gear is basic driving technique.

Even if hundred threads in tbhp tells me to coast in neutral I will never do.
This is something that cannot be left to an individual's style or will.
Someone coasting in neutral gear affects everyone around.

[attinder]

Originally Posted by fordday

Someone coasting in neutral gear affects everyone around.

Agreed, Engine may stall compromising brakes and steering.

[arvind71181]

Originally Posted by attinder

Agreed, Engine may stall compromising brakes and steering.

Coasting in Neutral means the vehicle will never stall, as there are no gears involved in the drive at all. You don't get engine braking and you cannot accelerate suddenly are probably the main reasons to avoid coasting in Neutral

[Aroy]

Originally Posted by AjayJoshuaN

When I travel from Chennai to Trivandrum, I usually reach 100km/h and coast in neutral to 80 km/h and repeat this. Sometimes I would reach to 110km/h or 120 km/h and coast in neutral to 100 km/h as needed and repeat this.

The AFE shows 20Km/L on my Xylo.
I never need to stop on the way anywhere for refuelling when I coast in neutral.

....................

That coasting saves fuel is a fallacy, more of an urban myth.

While coasting the fuel consumption is same as idling which is quite high. On the other hand driving in gear with and extra light foot, while maintaining constant speed, reduces the fuel consumption to less than idling. Plus you get the following advantages :

1. Full control of the car as you can accelerate and decelerate instantaneously.
2. Engine braking for emergency.

In many fiction, movies and serial the car just does not respond and brakes are disabled. In such a scenario engine braking can save your life, where as coasting will be your doom.

[AjayJoshuaN]

Originally Posted by Aroy

That coasting saves fuel is a fallacy, more of an urban myth.

While coasting the fuel consumption is same as idling which is quite high. On the other hand driving in gear with and extra light foot, while maintaining constant speed, reduces the fuel consumption to less than idling. Plus you get the following advantages :

1. Full control of the car as you can accelerate and decelerate instantaneously.
2. Engine braking for emergency.

In many fiction, movies and serial the car just does not respond and brakes are disabled. In such a scenario engine braking can save your life, where as coasting will be your doom.

Unfortunately this cannot be swept away as a myth or fallacy, as I said, because the evidence of not needing to refuel on a journey > 700 km stands out loud and clear.

The point is not about how much fuel is consumed when idling versus engine braking. It is more about destroying the work done by the fuel. Engine braking destroys work done by fuel.


The same is the case in electric cars as well. Coasting takes priority over regen, because regen inevitably leads to losses
https://thebrakereport.com/intellige...e-new-vw-id-4/

People who are not used to coasting will definitely "feel" a bit out of control. It needs a bit of getting used to and adaptation.

[gupta_chd]

I feel it is best to use Cruise Control instead of Coasting or other things provided it is available in your car. As I have seen numerous times, it increases the mileage by atleast 15-20% provided you are able to use it for some good distance. Gives relief to foot as well.

[Aroy]

Originally Posted by AjayJoshuaN

Unfortunately this cannot be swept away as a myth or fallacy, as I said, because the evidence of not needing to refuel on a journey > 700 km stands out loud and clear.

...................

As far as I remember, studies were carried out in US regarding this very issue. What was found is that the fuel used while cruising in gear at an optimum speed was much less than fuel used while coasting in neutral (idling).

https://www.popularmechanics.com/car...-fuel-economy/

https://practicalmotoring.com.au/car...can-save-fuel/