Shifting to Neutral on an A/T - Better FC?

[jut703]

Using the same car, in the same driving conditions, my mother garners 6.6-7.1 km/l. When my dad used the car for a week, his average was 8-9 km/l, and they both pass the Makati-Pasig route. This is despite the fact that he drives at an average speed 20 kph faster and has occasional bursts of boy racer tendencies.

I would attest the lower FC of my dad to the fact that he keeps a more constant and less hasty acceleration from standstill, but he also does one quirky thing - he frequently puts the car in Neutral when coasting.

Is this bad for the car? It's an Altis 2.0V A/T. Also, I've noticed that when taking the foot off the gas, the rev drops to 1000 rpm. Does that mean that even in D, when the pedal is disengaged, the car goes to neutral? In other words, is the act of shifting to N every time you coast unnecessary?

And, does shifting to N actually help improve fuel economy? If so, at what cost? Does it drastically increase the wear and tear of the transmission?

I'd just like to be informed, so that I'll know if I should follow it or if I should advise him to stop, especially since my mom now does the same thing too after I told her my dad gets better mileage.

[KinKyHOOTER]

Using the same car, in the same driving conditions, my mother garners 6.6-7.1 km/l. When my dad used the car for a week, his average was 8-9 km/l, and they both pass the Makati-Pasig route. This is despite the fact that he drives at an average speed 20 kph faster and has occasional bursts of boy racer tendencies.

I would attest the lower FC of my dad to the fact that he keeps a more constant and less hasty acceleration from standstill, but he also does one quirky thing - he frequently puts the car in Neutral when coasting.

Is this bad for the car? It's an Altis 2.0V A/T. Also, I've noticed that when taking the foot off the gas, the rev drops to 1000 rpm. Does that mean that even in D, when the pedal is disengaged, the car goes to neutral? In other words, is the act of shifting to N every time you coast unnecessary?

And, does shifting to N actually help improve fuel economy? If so, at what cost? Does it drastically increase the wear and tear of the transmission?

I'd just like to be informed, so that I'll know if I should follow it or if I should advise him to stop, especially since my mom now does the same thing too after I told her my dad gets better mileage.

I don't thing putting the A/T to N will give dramatic increase to fuel consumption. You will actually waste the momentum you have gained from 1st, 2nd, 3rd, 4th gear....at 70kph, the VVTi will kick-in and it will limit your RPM between 1,500 - 1,800 RPM. So from that speed the VVTi is actually helping you conserve the energy and speed gained from accelration. Then after coasting at N from 80kph, you let the speed go down to 30kph...then put the tranny in D again and have the engine rev again and accelerate to 80kph. Sayang ang energy and momentum gained by the car. The Engine actually works the hardest while accelerating, and having a heavy foot to couple it with will result in bad fuel mileage.

Two additional things:
====================
1.) If you put A/T transmission to D from N while at speed (80kph example) will jolt the tranny as it engages the gears again and that is also not good.

2.) Coasting at N will also be dangerous as it will not have engine brakes.

I think the better fuel mileage your dad is getting is a result of him having a lighter foot on the gas pedal compared to your mom.

[ParticleX]

i coast also (going N on downhills) on a terrano to help the turbo cool it down, but sometimes i worry about the brakes will conk out anytime (with the huge weight of the vehicle ). i think it would be better to stay with D, the fuel savings is not worth it compare to an engine brake, who knows what will happen.

[HardCharger]

I read somewhere that doing this is bad for the transmission.

It has something to do with the tranny fluid circulation and the sudden load thing mentioned.

It's also discouraged because of the also mentioned lack of engine breaking.

[niky]

Going downhill, it's better to leave it in gear. With your foot off the gas and the throttle plate closed, your engine is either using miniscule amounts of fuel or absolutely no fuel (if it's EFI, the injectors shut off completely on coast-down).

For this reason, actually shifting to N while driving doesn't really help much... unless you're practicing hypermiling and using the "Pulse and Glide" method. (which also requires you to turn off your engine... ). If you're coasting to a slow stop, coasting in gear once you're below around 60 km/h uses no gas, whereas if you're coasting in neutral, you'll use more fuel because your engine is still idling.

Shifting to neutral does help, though, at a stop or in stop-go traffic... at a stop, your torque converter is under load, straining against your brakes. In stop-go traffic, putting it in "N" after you move allows you to coast a bit farther with just a little tap of the gas.

Many nay-sayers say that the extra motion wears down the mechanism... but if the torque converter is disengaged when you shift, there's really no issue.

[jut703]

I don't thing putting the A/T to N will give dramatic increase to fuel consumption. You will actually waste the momentum you have gained from 1st, 2nd, 3rd, 4th gear....at 70kph, the VVTi will kick-in and it will limit your RPM between 1,500 - 1,800 RPM. So from that speed the VVTi is actually helping you conserve the energy and speed gained from accelration. Then after coasting at N from 80kph, you let the speed go down to 30kph...then put the tranny in D again and have the engine rev again and accelerate to 80kph. Sayang ang energy and momentum gained by the car. The Engine actually works the hardest while accelerating, and having a heavy foot to couple it with will result in bad fuel mileage.

Two additional things:
====================
1.) If you put A/T transmission to D from N while at speed (80kph example) will jolt the tranny as it engages the gears again and that is also not good.

2.) Coasting at N will also be dangerous as it will not have engine brakes.

I think the better fuel mileage your dad is getting is a result of him having a lighter foot on the gas pedal compared to your mom.

He only coasts during, for example, on the downhill part of the flyover. Shifting back from N to D right after doesn't give any jolt as you say. Or are you talking about a jolt unfelt by occupants but present in the transmission?

The issue about wasting energy on acceleration after shifting back to D isn't actually much of an issue, particularly because he shifts to N mostly when going downhill, where the car even accelerates, or if he's slowing to a stop (For example a stop light, around 500m from it he releases the gas, shifts to N, and brakes to a stop).

Going downhill, it's better to leave it in gear. With your foot off the gas and the throttle plate closed, your engine is either using miniscule amounts of fuel or absolutely no fuel (if it's EFI, the injectors shut off completely on coast-down).

For this reason, actually shifting to N while driving doesn't really help much... unless you're practicing hypermiling and using the "Pulse and Glide" method. (which also requires you to turn off your engine... ). If you're coasting to a slow stop, coasting in gear once you're below around 60 km/h uses no gas, whereas if you're coasting in neutral, you'll use more fuel because your engine is still idling.

Shifting to neutral does help, though, at a stop or in stop-go traffic... at a stop, your torque converter is under load, straining against your brakes. In stop-go traffic, putting it in "N" after you move allows you to coast a bit farther with just a little tap of the gas.

Many nay-sayers say that the extra motion wears down the mechanism... but if the torque converter is disengaged when you shift, there's really no issue.

So from my understanding, for example going down a flyover, and I'm going at 80 kph. If I just release the accelerator, I wouldn't be feeding my engine more fuel even if the downhill slope increases my speed to about 100 kph? In other words, I don't need to shift to neutral to cut the fuel off since it does so already as long as I keep my foot off the accelerator? And in fact, if I understand correctly, keeping it in neutral uses more fuel because of the idling?

And does going through successive humps count as stop and go. There's this street near our place where there are about 7 humps in a 500 meter stretch, and what he does, upon approaching the hump, shifts to N, then once the car overcomes the hump, shifts to D, taps on the gas a little just to keep the car moving, then shifts back to N and coasts until the next hump. Is this better for mileage or is it just better to keep coasting?

In fact, I don't really understand the concept of Neutral and Drive that much when it comes to how it consumes fuel. If I am moving and I put the car in neutral, I'm using the same amount of gas as I would if I were idling on a stoplight, yes? But, releasing the gas pedal while in D completely cuts fuel supply to the engine? Is that why, when I'm driving, whatever the slope, as long as I coast while in D, my revs go down to 1000 rpm? I mean, driving a manual and releasing the gas keeps the rpm at whatever rpm it is until it slowly decelerates. Apparently it's not the case for automatics and I don't particularly understand why.

[mreyes]

sir niky,

is this called hypermiling? ginagawa ko rin ito pero nung nabasa kong nakakasira ng auto tranny, di ko na ginagawa. lagi na lang akong nasa D, and would only put it in neutral pag trapik or pag nakahinto sa trapik light.

[Type 100]

So from my understanding, for example going down a flyover, and I'm going at 80 kph. If I just release the accelerator, I wouldn't be feeding my engine more fuel even if the downhill slope increases my speed to about 100 kph? In other words, I don't need to shift to neutral to cut the fuel off since it does so already as long as I keep my foot off the accelerator? And in fact, if I understand correctly, keeping it in neutral uses more fuel because of the idling?

One big yes.

And does going through successive humps count as stop and go. There's this street near our place where there are about 7 humps in a 500 meter stretch, and what he does, upon approaching the hump, shifts to N, then once the car overcomes the hump, shifts to D, taps on the gas a little just to keep the car moving, then shifts back to N and coasts until the next hump. Is this better for mileage or is it just better to keep coasting?

No, that does not count as stop-and-go. Think about it: you're not coming to a complete stop every time you come across a hump. You WANT to press the throttle to crest the hump and go along your merry way, so why would you want to put it in Neutral in that situation?

It doesn't make sense. If anything it overcomplicates things. The less you have to fiddle with the controls, generally the better for the car.

[KinKyHOOTER]

He only coasts during, for example, on the downhill part of the flyover. Shifting back from N to D right after doesn't give any jolt as you say. Or are you talking about a jolt unfelt by occupants but present in the transmission?

The issue about wasting energy on acceleration after shifting back to D isn't actually much of an issue, particularly because he shifts to N mostly when going downhill, where the car even accelerates, or if he's slowing to a stop (For example a stop light, around 500m from it he releases the gas, shifts to N, and brakes to a stop).

Ah I see. So your dad is just doing the coasting before every stoplight Stops. Well actually it does make the engine consume less gas, but not that much at all compared to having it in D before every stoplight Stops. No major gains really as I see it.....its the same with going from D to N before every humps.

But its actually dangerous, because if you need to do sudden
maneuvers you wont be able to do it because your in N.

The jolt to the tranny thing that I mentioned was because I thought your dad was coasting from stop up to a speed (ex: 80kph) then putting it to N then after the speed gets slower he puts it to D again, the driver will feel a little jolt once the gear engages again. Nothing disastrous really, but I feel its not good for the tranny...I understood your question wrongly earlier

----> Yes, putting the car to N is in the same state as if your idling in your garage or on every stoplight.

----> While in D, even if you dont step on the gas the automatic tranny is still engage. On a level ground, it will still move even if you dont step on the gas........I'm not very sure, but I think it still consumes gas and still has a 4th gear engine brake effect. Please correct me if I'm wrong.

[Type 100]

But its actually dangerous, because if you need to do sudden
maneuvers you wont be able to do it because your in N.

The jolt to the tranny thing that I mentioned was because I thought your dad was coasting from stop up to a speed (ex: 80kph) then putting it to N then after the speed gets slower he puts it to D again, the driver will feel a little jolt once the gear engages again. Nothing disastrous really, but I feel its not good for the tranny...I understood your question wrongly earlier

Agreed on the inability to do sudden maneuvers.

Shifting from N to D at speed is also not good for your A/T. On a manual gearbox you could blip the throttle before re-engaging the clutch to avoid driveline wear, but on an A/T the clutch is permanently engaged.

[sachiel]

Gravity is acceleration so it will always be good for the economy of the car (just have good breaks). I only shift to N when I know I will be hitting full stop from slopes or traffic as it gives less stress to the breaks.

[jut703]

Ah I see. So your dad is just doing the coasting before every stoplight Stops. Well actually it does make the engine consume less gas, but not that much at all compared to having it in D before every stoplight Stops. No major gains really as I see it.....its the same with going from D to N before every humps.

But its actually dangerous, because if you need to do sudden
maneuvers you wont be able to do it because your in N.

The jolt to the tranny thing that I mentioned was because I thought your dad was coasting from stop up to a speed (ex: 80kph) then putting it to N then after the speed gets slower he puts it to D again, the driver will feel a little jolt once the gear engages again. Nothing disastrous really, but I feel its not good for the tranny...I understood your question wrongly earlier

----> Yes, putting the car to N is in the same state as if your idling in your garage or on every stoplight.

----> While in D, even if you dont step on the gas the automatic tranny is still engage. On a level ground, it will still move even if you dont step on the gas........I'm not very sure, but I think it still consumes gas and still has a 4th gear engine brake effect. Please correct me if I'm wrong.

Well of course at a stop, the torque converter would still be working hence the minute movement of the car when you put it at D even without stepping on the gas.

So the issue really is if going in neutral early is better for the car or if it would be just as beneficial to coast the same way but in D and then just engage N once the vehicle stops.

[meledson]

I think it will be better to keep it at "D". mas mahal pag nasira ang transmission.

never pa akong nag shift to "N" while still moving.

[speed unlimited]

Kung talagang hindi gumagalaw traffic mas mainam ilagay mo na lang sa neutral .

[yapoy86]

put to neutral while in traffic is good to lessen the strain on the transmission and the brakes..

putting the transmission at N while moving will not damage the transmission as long as the engine is running..

the engine drops at idle when you release the accelerator is due to the torque converter.. unlike in manual, the engine is connected directly to the transmission while in automatic, the medium is liquid which is the ATF. you will not feel the engine break in A/t unless you force the transmission to downshift

[niky]

sir niky,

is this called hypermiling? ginagawa ko rin ito pero nung nabasa kong nakakasira ng auto tranny, di ko na ginagawa. lagi na lang akong nasa D, and would only put it in neutral pag trapik or pag nakahinto sa trapik light.

Yup.

In fact, I don't really understand the concept of Neutral and Drive that much when it comes to how it consumes fuel. If I am moving and I put the car in neutral, I'm using the same amount of gas as I would if I were idling on a stoplight, yes? But, releasing the gas pedal while in D completely cuts fuel supply to the engine? Is that why, when I'm driving, whatever the slope, as long as I coast while in D, my revs go down to 1000 rpm? I mean, driving a manual and releasing the gas keeps the rpm at whatever rpm it is until it slowly decelerates. Apparently it's not the case for automatics and I don't particularly understand why.

The answer is "it depends".

It depends on the speed and the situation. Sometimes it's better, sometimes it's not. Hypermilers have scangauge tools and complex calculations that show them when it's best to coast in neutral or in-gear. Your rpm will only drop down to 1000 rpm in-gear on an automatic when the car either drops to idle or if it goes into OD (high gear). The former uses a little more gas than coasting in OD. Coasting in OD uses none.

-

Humps? Pocholo Ramirez before shared this tip with the guys on the Xtra Mile challenge. Don't brake for humps.

-

In general, it's actually better to coast down a flyover in-gear (preferably OD)... you'll still accelerate going downhill, gaining momentum, and while you're in gear, you're using virtually no fuel at all. The momentum of your vehicle is running your engine, your alternator and your power steering pump.

Personally, I only disengage if I'm far away from a light and it's red already. If the light is just turning red, I leave it in gear for the stronger engine braking. Then I put it in neutral when I'm stopped.

Honestly, shifting to N doesn't damage the transmission. At least, nowhere near as much as the heat-build-up of leaving it in D in noon-day traffic does.

[nadeem1414]

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[jut703]

I tried comparing coasting in D and N, as well as doing some research about it.

The feature niky was talking about is apparently called DFCO (Deceleration Fuel Cut Off), and is present in practically all new cars (A/T or M/T). However, when trying it on normal driving conditions, I noticed that coasting in D makes my engine stay at somewhere around 1200 rpm, as compared to in N, where it goes down to 900-1000. I'm quite convinced that DFCO works, but I can't convince my dad to believe in me because of the higher idle figure.

I tried explaining it to him, and from what I understand, the higher rpm is because its the wheels running the engine, not because the engine is burning fuel. Is this correct? What's the real deal?

Also, I noticed that even if DFCO is engaged in my car, I still engine brake more than if it was in N. Hence, if I don't need to lose speed but want to use gravity to keep my car moving, it appears that N is better. Is there some truth to this or am I missing a fundamental concept?

And how do I compare the consumption? On the downhill part of a flyover, coasting in N or D both give 50-99 km/l from the car's trip computer. :|

[niky]

I tried comparing coasting in D and N, as well as doing some research about it.

The feature niky was talking about is apparently called DFCO (Deceleration Fuel Cut Off), and is present in practically all new cars (A/T or M/T). However, when trying it on normal driving conditions, I noticed that coasting in D makes my engine stay at somewhere around 1200 rpm, as compared to in N, where it goes down to 900-1000. I'm quite convinced that DFCO works, but I can't convince my dad to believe in me because of the higher idle figure.

I tried explaining it to him, and from what I understand, the higher rpm is because its the wheels running the engine, not because the engine is burning fuel. Is this correct? What's the real deal?

Also, I noticed that even if DFCO is engaged in my car, I still engine brake more than if it was in N. Hence, if I don't need to lose speed but want to use gravity to keep my car moving, it appears that N is better. Is there some truth to this or am I missing a fundamental concept?

And how do I compare the consumption? On the downhill part of a flyover, coasting in N or D both give 50-99 km/l from the car's trip computer. :|

True. The wheels are turning the engine, that is why the rpm is slightly higher.

And yes, true... since the engine isn't running, it's dragging the vehicle speed down (this is known as engine-braking). Yes, if you don't want to slow down, you can pop it in N to coast further.

[softop]

"he frequently puts the car in Neutral when coasting."

It's not worth it unless it saves your Dad a significant amount of fuel/distance travelled. I would put "significant" at at least 50% -enough savings to at least pay for your Dad's auto insurance. Most experts or long-time drivers would say it's "delikado" pa nga. (IMHO)