[Aroy]

When you stop pressing the accelerator, the quantum of fuel injected is reduced drastically, and you get the engine assisted deceleration as a bonus. (I have checked it on our new City, where the MID goes wild if the foot is taken off the accelerator for a few seconds - FE goes > 40km/l)

When ever feasible, I progressively down shift so that the use of breaks is minimal. This is a habit born out of necessity, as in the good old Ambassador days, the brakes failed quite regularly.

I remember driving my BIL's car to the mechanic, when its brakes had failed completely. It was tough but doable and I managed to stop the car every time using the gearbox supplemented by the hand break for the final stop (in the older cars you can also switch the engine off to stop it.

[mayankk]

Over the past few months, I have consciously started using engine braking, unless it's bumper to bumper traffic, in which case it's impossible.
One, it's made me more aware of distances to maintain, and I feel it has helped me avoid a few scrapes.
And two, from 12kmpl last winter, this winter I'm averaging between 13.5-14.

If you have a newer vehicle, which shows instantaneous consumption, you'll easily be able to make out that no accelerator at anything more than something like 1.5-2 times the idle setting will see the meter max out, which typically means no, or absolutely minimum fuel going in.

[Modifiedsachin]

Originally Posted by anupam00

Hi
To my opinion there is no problem regarding shifting of gears from 5th to nuetral at the speed of 80,100.. watever... Nothing happens to your car balance or ur barkes if you do it. moreover it would be good for your car mileage.

whether it is a expressway or downhill ensure that your engine is on.. that wat really matters. rest all is fine if u are comfortable in doing so.

Initially even i was of this opinion.

But when I saw the difference myself I believed.

When I deep press the clutch or make neutral (Both are same in my opinion), the car is free & its weight and the speed combined together gives a momentum which will be a big load on breaks while breaking on down hills, though on straight road the effect is less.

My breaking distance was longer than the car in gear. also the response was quick and was much confident about the breaking than in neutral condition.

Again on higher speeds, when you have a slope (Not down hill) on straight road, or a steady straight road, then by making neutral, I feel that I save fuel, by allowing the car to gain momentum or continue the momentum without applying any acceleration.

But after reading more posts, I feel that newer cars give minimum fuel if acc is not pressed even when in gear. Will check the inst. avg in my linea today.

[sgiitk]

Let me put in a few straight facts, this has nothing to do with consumption but ma have to do with survival.

The Golden rule - the car should always be in proper gear with engine running.

Going downhill, the proper gear is the same as for going up that slope.

Remember you are on the road with four rubber patches of the same size as approx. size 8 shoes. Proper control both steering and engine is a MUST.

[pganapathy]

In terms of mileage you are better off coasting in gear rather than neutral. The logic is simple. If you are in neutral, your engine needs to be ticking over at say 800 to 1,000 rpm, which means you need petrol to keep the engine running. If you are in gear but not accelerating, then the engine is not using any fuel as you are not pressing the accelerator and thus the fuel injector does not open at all.

Of course, unless you are doing a lot of driving this difference is minimal. Purely because you very rarely get to the situation where you are cruising for large distances in neutral or with your foot off the accelerator. The only possible exception is down a hill.

With regards to safety, the moment you put the vehicle in neutral, you remove engine braking from the equation, which means you need longer to stop. Never a good thing

[racer_ash]

Originally Posted by pganapathy

In terms of mileage you are better off coasting in gear rather than neutral. The logic is simple. If you are in neutral, your engine needs to be ticking over at say 800 to 1,000 rpm, which means you need petrol to keep the engine running. If you are in gear but not accelerating, then the engine is not using any fuel as you are not pressing the accelerator and thus the fuel injector does not open at all.

By this logic, even while idling, we are not pressing the accelerator. That doesnt mean that idling does not require fuel. The same logic would apply for coasting in gear as well. A minimum amount of fuel would be consumed and I think this is atleast equal to that used while idling.

I distinctly remember an experiment in Mechanical Engineering about the amount of fuel used by engines under different operating conditions and hence my clarification. Ofcourse that was with the old carburettor type engine. I am sure it will apply to the modern FI engines as well.

[RM2488]

Originally Posted by racer_ash

By this logic, even while idling, we are not pressing the accelerator. That doesnt mean that idling does not require fuel. The same logic would apply for coasting in gear as well. A minimum amount of fuel would be consumed and I think this is atleast equal to that used while idling.

I distinctly remember an experiment in Mechanical Engineering about the amount of fuel used by engines under different operating conditions and hence my clarification. Ofcourse that was with the old carburettor type engine. I am sure it will apply to the modern FI engines as well.

Your statement is valid only for older generation cars. In some newer cars, the injectors can go down to 0% duty cycle when the ECU senses the wheels are driving the engine (such as on a slope in gear). Thus, you'll consume less fuel to go down a slope in-gear (with less braking required as well) than descending it in neutral.

[mayankk]

Originally Posted by racer_ash

By this logic, even while idling, we are not pressing the accelerator. That doesnt mean that idling does not require fuel. The same logic would apply for coasting in gear as well. A minimum amount of fuel would be consumed and I think this is atleast equal to that used while idling.

I distinctly remember an experiment in Mechanical Engineering about the amount of fuel used by engines under different operating conditions and hence my clarification. Ofcourse that was with the old carburettor type engine. I am sure it will apply to the modern FI engines as well.

http://www.popularmechanics.com/_mob...l-fuel-economy


Basically, in normal motion, the engine drives the wheel, but being in gear while coasting, or under engine braking, the wheels drive the engine.

[Shanksta]

When I drive on the highways if I have to slow down I just let go of the accelerator and let the engine braking do it's job and only before the car jerks I depress the clutch.Also when I brake on the highways I don't depress the clutch until the same situation as above arises.

But in the city I don't shift to the neutral gear when approaching the signal until the I stop the car at the signal and once my car is stationary I shift to neutral and engage the handbrake.Also while braking in the city I also simultaneously depress the clutch.

The reason being on the highways for the speeds we do we require the most braking efficiency. But in the city for the 30-50 km/hr we do we don't require that much braking efficiency until the need arises,also simultaneously depressing the clutch while braking in the city provides a smoother ride and stop for the co-passengers.
Just my 2 cents

[(Alok)]

Originally Posted by mayankk

or under engine braking, the wheels drive the engine.

What are the adverse effects on engine in this situation?

[mayankk]

Originally Posted by (Alok)

What are the adverse effects on engine in this situation?

Presumably none, unless you shift into such a low gear that the ratio pushes the revs in upper or red range. Like shifting at 80 kmph from 4th to 2nd.

[Denis]

Never Ever shift to neutral before braking; this sends your car into a free-motion which coupled with the fact that the engine is no longer controlling the speed at which your tyres turn could put you in a dangerous situation, and could also lead to brakes totally failing on downhill inclines.

[(Alok)]

We are discussing a very basic thing here. It is just like ‘press the clutch while changing the gear’.

If a person does this (Shifting to Neutral or Pressing the Clutch when Braking), he should join motor driving school to learn driving. Just holding the steering and pushing the accelerator is not enough.

[chetanthaker]

When you plan on slowing down or are going downhill, put your car in the highest gear available and let it cruise. You will use zero fuel while doing so. Slow down to about 20kmph, and at a safe distance, press clutch and go to neutral or your desired gear

Source: Top Gear

[saket77]

Originally Posted by chetanthaker

When you plan on slowing down or are going downhill, put your car in the highest gear available and let it cruise. You will use zero fuel while doing so. Slow down to about 20kmph, and at a safe distance, press clutch and go to neutral or your desired gear

Source: Top Gear

I tend to differ...& many others will. The golden rule of coming downhill is that use the same gear that you would have used to climb the same hill. This provides proper engine braking & you don't want to burn your brake pads, esp while coming downhill. Frequent use of brakes, like those while coming downhill produces 'brake fading' which is loss in braking efficiency. This brake fad can actually result in brake failure.