Is it OK to coast in Neutral for Better fuel economy?

[BigB]

I live north of the GTA with several hills with longer grades. I have a new 3 GS SKY AUTO and like to shift it into N and coast down the hills for better fuel economy - it does coast well and burns hardly any fuel, plus the engine isn't being used except to idle.

Is doing this OK? Am I harming the engine in any way?
Thanks :D

[Thrizzl3]

It uses fuel to idle. But you're driving a skyactiv..just keep in Drive when slowing down.

[Hyperion]

It uses less fuel in gear with your foot off the throttle as momentum is moving your engine as opposed to having fuel injected

[p-o-g-i]

In this situation, I can't see that much fuel being saved.

[BigB]

True that it's using fuel to idle, although I have noticed that when in N, it's using much less coasting down a hill AND the engine isn't slowing the car down. This is the main reason for keeping in in N - it coasts without any interference from the engine - in N it just coasts and picks up a lot of speed while using about 1.5l/100km; in D the engine slows the car way down and uses closer to 3l/100kim. It seems like the better option to me....?

[Kiyomi]

True that it's using fuel to idle, although I have noticed that when in N, it's using much less coasting down a hill AND the engine isn't slowing the car down. This is the main reason for keeping in in N - it coasts without any interference from the engine - in N it just coasts and picks up a lot of speed while using about 1.5l/100km; in D the engine slows the car way down and uses closer to 3l/100kim. It seems like the better option to me....?

being in gear all the time is prob more important and safer than a little fuel economy. just my 2 cents.

[Thrizzl3]

True that it's using fuel to idle, although I have noticed that when in N, it's using much less coasting down a hill AND the engine isn't slowing the car down. This is the main reason for keeping in in N - it coasts without any interference from the engine - in N it just coasts and picks up a lot of speed while using about 1.5l/100km; in D the engine slows the car way down and uses closer to 3l/100kim. It seems like the better option to me....?

If you're going down a hill put the car in manual mode and leave it in gear 3 or 4. you'll notice that the car uses 0.0L of fuel during that time.

[brucewayne]

being in gear all the time is prob more important and safer than a little fuel economy. just my 2 cents.
+1

[silverstarmazda]

and jamming the car back into D while the car is in motion isnt exactly really good for anything.

[Booter22]

i would say no. i know its a big read.. but on section 5 - 13 of the owners manual ( for the 2010 ) which im sure is similar to the others, but under starting and driving about automatic transaxle controls it says:

Do not shift in to N when driving the vehicle : shifting into N while driving is dangerous. engine braking cannot be applied when decelerating which could lead to an accident or serious injury.

Caution:
Do no shift into N when driving the vehicle doing so can cause transaxle damage.

[TheMAN]

coasting in neutral does NOTHING to improve gas mileage but in fact the opposite... engines run notoriously inefficient at idle and burn more gas than at say 2000rpm due to volumetric efficiency and thus leading to combustion efficiency... if you looked at the trip computer, it will show infinite km/h because it really is so

you are better off coasting in gear as the ECU turns off the fuel injectors during coasting until you step on the pedal again or if RPMs are low enough that it has to kick the injectors back on to keep the engine from stalling
I'm still in the middle of training my dad that coasting at high RPMs doesn't hurt gas mileage but in fact improves it when he feels like he needs to use engine braking... often he shifts back to a higher gear to keep RPMs low on twisty roads and hills.... in the old days with carburetted engines, fuel is being squirted no matter what so that is what he is used to and in that case, lower RPMs is always better, which means in other words, idling in neutral to coast in an old carburetted car is better than keeping it in gear.... I find this habit still being used often in 3rd world countries with modern vehicles because they've been used to carburetted engines far longer than we have

this is all besides the fact that if you're coasting down a steep hill on a winding road is very dangerous when you're out of gear... you can overheat the brakes and lose control of the car... it is safer to stay in gear, even in "D", but using a lower gear on hilly winding roads is always the best to maintain control of the car, regardless of whether you're driving an automatic or manual... most people don't know how to engine brake because they were never taught this in driver's ed

[-cj-]

This only applies to Mazda3's with direct injection (IE: Mazdaspeed3/6, and the SkyActive engines). First generation Mazda3's were port injection which won't shut off the injectors while coasting.

[TheMAN]

yes it does!
ALL EFI cars do it, regardless of method
if it didn't do it, you'll get horrendous back fires when you let off the gas!

even 25 year old mazdas do this.... if you had a data logger, you'll see that the injector duty cycles are 0 during coasting and they kick back on at around 1200rpm

[-cj-]

Wow I can tell that you are passionate about this subject.

I was under the impression that DI was the only type of engine (aside from diesels) that truly shuts off fuel injection during coasting in gear. But I could be wrong.

[TheMAN]

passionate? really?

[2013_M3]

being in gear all the time is prob more important and safer than a little fuel economy. just my 2 cents.

+2

[BigB]

So I read the manual for the 2013 and says the same as what Booter quoted: Do not shift in to N when driving the vehicle : "shifting into N while driving is dangerous. engine braking cannot be applied when decelerating which could lead to an accident or serious injury. Caution: Do no shift into N when driving the vehicle doing so can cause transaxle damage."

So will no longer coast in N and if need be will manually set to a higher gear and coast with low RPM's...I might give that a try.
Thanks all for the posts.
BB

[silverstarmazda]

chiming in: 2004 manual says that too

[WHO]

I do have a tendency to slap her into neutral in the city while approaching a red light or other stoppage. Driving a stick shift, it's just a PITA to downshift, gear by gear. If I know I'm coming to a stop and not speeding up for a while, I'll just put in in neutral.

But, I agree about coasting, just leave it in gear. I'm guilty of sometimes applying the clutch in such cases, but you know what they say : do as I said, not as I do. When I do apply the clutch and drop in neutral, if I end up accelerating before stopping, I rev the engine back to matching engine speed BEFORE I re-engage the gear.

Pro tip: You'll save more gas avoiding hard/unnecessary accelerations and braking (looking far ahead, defensive driving) than by coasting in N.

[silverstarmazda]

also, read the traffic. its not just street designs that cause unnecessary fuel to be wasted.

[TheMAN]

what's said in the manual is just a cookie cutter instruction that ensures mazda is legally covered and not responsible for any owner stupidity... there is no engine or transmission damage by coasting in neutral, it's just a waste of gas to do that and dangerous down hill because you can over work the brakes... some transmissions do get damaged by just being revved in neutral... old volvos are something that come to mind... I don't recall any mazda trans that get damaged in neutral though... neutral behaves the exact same as "park", except the park pawl isn't engaged

[Noisy Crow]

If you have to suddenly manoeuvre (e.g. large critter runs across the road, on coming vehicle cross the centre line) you are screwed as you've reduced your options for avoiding or minimizing the impact.

[Lumberjack]

It also helps if you turn your mirrors in too :P

[Cab0oze]

coasting in neutral does NOTHING to improve gas mileage but in fact the opposite... engines run notoriously inefficient at idle and burn more gas than at say 2000rpm due to volumetric efficiency and thus leading to combustion efficiency... if you looked at the trip computer, it will show infinite km/h because it really is so

you are better off coasting in gear as the ECU turns off the fuel injectors during coasting until you step on the pedal again or if RPMs are low enough that it has to kick the injectors back on to keep the engine from stalling
I'm still in the middle of training my dad that coasting at high RPMs doesn't hurt gas mileage but in fact improves it when he feels like he needs to use engine braking... often he shifts back to a higher gear to keep RPMs low on twisty roads and hills.... in the old days with carburetted engines, fuel is being squirted no matter what so that is what he is used to and in that case, lower RPMs is always better, which means in other words, idling in neutral to coast in an old carburetted car is better than keeping it in gear.... I find this habit still being used often in 3rd world countries with modern vehicles because they've been used to carburetted engines far longer than we have

this is all besides the fact that if you're coasting down a steep hill on a winding road is very dangerous when you're out of gear... you can overheat the brakes and lose control of the car... it is safer to stay in gear, even in "D", but using a lower gear on hilly winding roads is always the best to maintain control of the car, regardless of whether you're driving an automatic or manual... most people don't know how to engine brake because they were never taught this in driver's ed

+1, that sums the whole topic up. It uses more gas and it could potentially be dangerous... end of story.

[TheMAN]

It also helps if you turn your mirrors in too :P

no it doesn't... that is a common misconception
mirrors folded in gives greater air turbulence around the mirrors as when folded in they are not aerodynamically shaped... the only way you will achieve better aerodynamics is to remove them and put a blanking plate altogether
mirrors folded out is what the car designers have made them to be for the best aerodynamics from their wind tunnel testing

not to mention, mirrors folded in is unsafe and possibly illegal

[Cab0oze]

no it doesn't... that is a common misconception
mirrors folded in gives greater air turbulence around the mirrors as when folded in they are not aerodynamically shaped...

Well it probably does a bit, less profile drag, but not really worth mentioning. Also, I think he was being sarcastic...

[stock3]

Coasting in a manual transmission, no problem. In an automatic it can cause problems long term, but how much, if any will depend on the manufacturer and other conditions. One thing is for sure, the trannys were designed to stay in D all the time, so it's safer to keep it that way.
If someone wants to shift stuff, they should get a manual and they can shift/control the tranny however they want. In computer controlled stuff it's better to let the automation do the work without any intervention.

[Booter22]

Coasting in a manual transmission, no problem. In an automatic it can cause problems long term, but how much, if any will depend on the manufacturer and other conditions. One thing is for sure, the trannys were designed to stay in D all the time, so it's safer to keep it that way.
If someone wants to shift stuff, they should get a manual and they can shift/control the tranny however they want. In computer controlled stuff it's better to let the automation do the work without any intervention.

im sure TheMAN can say there is a reason why not to do it in manual. but ive been driving 5sped for about 8 years, never have i once coasted in neutral. if for some reason you need to pick up speed, make an emergence move and cant get it back into gear for what ever reason.. your toast, that and it helps with engine braking, so when your going down a hill you dont need to ride the brake pedal like the idiot in front of you. :bang

[sarujo]

^ Booter22

I never coast in neutral either...as you said for safety and efficiency. I prefer to coast in gear so the injectors turn off and save fuel - this doesn't happen when you are in Neutral (as stated). With over 76,000km, I am still at 7mm on my brakes. Hopefully they get low enough so I can change them and flush the brake fluid at the same time. At the rate I'm going will easily hit 5 years.. :chuckle

[Booter22]

^ Booter22

I never coast in neutral either...as you said for safety and efficiency. I prefer to coast in gear so the injectors turn off and save fuel - this doesn't happen when you are in Neutral (as stated). With over 76,000km, I am still at 7mm on my brakes. Hopefully they get low enough so I can change them and flush the brake fluid at the same time. At the rate I'm going will easily hit 5 years.. :chuckle

I know im at 96 000 km and still have 6mm on the pads. But when I change them its hawk pads stop tech rotors and stainless lines and a fluid flush I think cuz at this rate those wont need replacement untill wrll over 200 000

[sarujo]

I'm sticking with OEM rotors but going with EBC Green pads.

[Lumberjack]

Apparently it's NOT the "end of story..." :chuckle



+1, that sums the whole topic up. It uses more gas and it could potentially be dangerous... end of story.
Well it probably does a bit, less profile drag, but not really worth mentioning. Also, I think he was being sarcastic...

[m_bisson]

Driving stick, there are Hills where I can push the clutch pedal, coast down the hill, and make it all the way to the stop sign or turn that I need to take. Surely I'm using less gas by doing that than leaving it in gear. Okay, maybe no fuels is being used to coast in gear, but the drag from the engine actually slows my speed on these Hills and I need to keep constant pressure on the gas pedal to maintain the speed limit.

Note: I am not shifting into neutral and getting off the clutch pedal. I'm leaving it in gear, but disengaging the clutch.

[Kiyomi]

Driving stick, there are Hills where I can push the clutch pedal, coast down the hill, and make it all the way to the stop sign or turn that I need to take. Surely I'm using less gas by doing that than leaving it in gear. Okay, maybe no fuels is being used to coast in gear, but the drag from the engine actually slows my speed on these Hills and I need to keep constant pressure on the gas pedal to maintain the speed limit.

what the... you don't engine brake if you put the clutch in, even if your in gear.

[m_bisson]

what the... you don't engine brake if you put the clutch in, even if your in gear.

What the.... Ninja edit :D

[Kiyomi]

Driving stick, there are Hills where I can push the clutch pedal, coast down the hill, and make it all the way to the stop sign or turn that I need to take. Surely I'm using less gas by doing that than leaving it in gear. Okay, maybe no fuels is being used to coast in gear, but the drag from the engine actually slows my speed on these Hills and I need to keep constant pressure on the gas pedal to maintain the speed limit.

Note: I am not shifting into neutral and getting off the clutch pedal. I'm leaving it in gear, but disengaging the clutch.

again, this makes no sense lol....
why are you pushing the clutch pedal when coasting down a hill?
by disengaging the clutch/pushing it in, you are not using your engine to brake.

[m_bisson]

I'm saying that the engine brakes too much because the hill is not a ski slope, it's a residential Street. I want to make it to the bottom without pressing the gas pedal. My speed trickles down to nothing halfway down the hill if I don't disengage the clutch.

[sarujo]

Then blip the gas and upshift to a higher gear.


I'm saying that the engine brakes too much because the hill is not a ski slope, it's a residential Street. I want to make it to the bottom without pressing the gas pedal. My speed trickles down to nothing halfway down the hill if I don't disengage the clutch.

[Kiyomi]

I'm saying that the engine brakes too much because the hill is not a ski slope, it's a residential Street. I want to make it to the bottom without pressing the gas pedal. My speed trickles down to nothing halfway down the hill if I don't disengage the clutch.

thats what engine braking is for which is how a manual should be driven, which means you are downshifting too early or you dont have to if you are completely stopped halfway down a small incline.,

[peterm15]

Imo if you guys are concerned with saving the fraction of of fuel you may or may not be saving. Buy a ****ing hybrid.
Drive the way you should be driving or take the damn bus.

This to me is like tailgating a tractor trailer to save gas. Ok it may work but it puts you right at the bottom of the darwin list

[TheMAN]

if you're so concerned about a little 200m stretch of road going down a hill from your house, then just roll down it with your engine off like those crazy hyper milers and hope you don't have to slam on your brakes hard to avoid some kid or a dog
otherwise, if it's a long hill and you're whining about engine braking slowing down your car too much, then just coast down in 5th gear WITHOUT stepping on the clutch pedal

coasting down hill with your foot in the clutch is no different than coasting down hill in neutral... it's stupid, wears clutch components, and wastes gas

[m_bisson]

Lol what's your problem? I'm trying to come up with a scenario where coasting in-gear is worse than coasting I neutral. Stop being so "Internet fighty" and try to see it from a different perspective.

[Hyperion]

There are no different perspectives,

[WHO]

Lol what's your problem? I'm trying to come up with a scenario where coasting in-gear is worse than coasting I neutral. Stop being so "Internet fighty" and try to see it from a different perspective.

haha settle down, I sometimes do it too (although I would typically just put in neutral in such a scenario where I know I'll be coming to a stop either way). But realize it's not the "right" or "wrong" way, by saying that you're playing the same game he's playing insulting hyper milers as well as eco-minded drivers, and suggesting we should all be driving our cars "like we stole it"... always be in gear and ready to speed up.

Suggesting to put it in 5th gear while you're going like 30 km/h *just* so you can purposely leave it in gear to cruise down a very slight slope is not practical at all. It's just trying to prove a point unnecessarily. And leaving it in 2nd or 3rd gear will slow you down too much, forcing you to give it gas. In this case, you're putting less wear on your entire drivetrain by simple putting it in neutral.

"Engines aren't meant to stop vehicles, brakes are"

[Kiyomi]

^^ one of the benefits of having a manual is engine braking and saving on wear and tear on other car parts such as brakes. by doing what you suggest, your probably losing more money in other parts than saving money on fuel. might as well get an automatic. putting it into another perspective,

its like putting an automatic in neutral while driving down a small hill. why do it? for one, its less safe to be out of gear. two, how much fuel are you actually saving if any and is it worth the extra risk?

being in gear all the time doesn't mean drive it like you stole it, it means your in control of your vehicle at all times. whos the more dangerous driver, the one who stays in gear, or the one who puts it in neutral?

or try pulling that on a road test. then tell the instructors that they are wrong for failing you for getting better fuel mileage. :D

[Booter22]

^^ one of the benefits of having a manual is engine braking and saving on wear and tear on other car parts such as brakes. by doing what you suggest, your probably losing more money in other parts than saving money on fuel. might as well get an automatic. putting it into another perspective,

its like putting an automatic in neutral while driving down a small hill. why do it? for one, its less safe to be out of gear. two, how much fuel are you actually saving if any and is it worth the extra risk?

being in gear all the time doesn't mean drive it like you stole it, it means your in control of your vehicle at all times. whos the more dangerous driver, the one who stays in gear, or the one who puts it in neutral?

or try pulling that on a road test. then tell the instructors that they are wrong for failing you for getting better fuel mileage. :D

Game.. set.. match.^^ (one day im sure we will see someone on the forum who does this as regular practise and make a thread about an accident they got in because they couldnt aviod it with there car in neutral or accelerate fast enough with the clutch in.. :bang )

i really am surprised this topic is still going. :chuckle

But sure lets coast in neutral to save.. fuel?? but need to use the brakes more, or hey WHAT ABOUT THE WEAR ON FLUIDS LIKE BRAKE OR TRANS with all the clutch in gear shift nonsense?.. i mean no one has brought that up..

annnnndddd FIGHT!

[TheMAN]

if it's "impractical" to coast in 5th gear for a small hill, then just keep in whatever lower gear you're in and if you have to maintain speed by stepping on the gas, DO IT
as I already explained before, the engine runs more efficient at RPMs that are NOT idle speed... so whether it's 2000, 3000, or 4000rpm, it'll still use less fuel if your foot is feather light to maintain speed than if you're coasting down a hill clutched in or neutral (same difference) at 800rpm

don't understand it? then go read up on fluid dynamics, intake and exhaust charge scavenging
nobody builds car, truck and bike engines that gets maximum efficiency at idle speeds because nobody drives at literally a snail's pace... want an engine that does that? get a generator engine, they never vary RPMs! companies build car, truck and bike engines optimized for a certain RPM range for best efficiency, that's how they achieve the good gas mileage ratings, simple as that
lower RPMs is never necessarily better MPGs... old habits die hard

[WHO]

The wear argument is very weak. You wear on the tranny/engine a lot more by engine braking, and downshifting 2 or 3 gears as you slow down, than just coasting in neutral which wears what? ... oh yeah! Nothing!

Brake pads cost much less than a clutch. So I'll use my brakes any day over my clutch to brake. I wouldn't be surprises to see the gas savings surpass the brake cost. BTW this comes from from seasoned race car drivers. On the track, the saying goes (as previously quoted) "brakes are meant to stop cars, not engines, which are meant to propel the car". The better technique on the track is to use the heel/toe technique to match the engine speed with the tranny... to AVOID unnecessary wear or worse: breakdown.

[Kiyomi]

The wear argument is very weak. You wear on the tranny/engine a lot more by engine braking, and downshifting 2 or 3 gears as you slow down, than just coasting in neutral which wears what? ... oh yeah! Nothing!

Brake pads cost much less than a clutch. So I'll use my brakes any day over my clutch to brake. I wouldn't be surprises to see the gas savings surpass the brake cost. BTW this comes from from seasoned race car drivers. On the track, the saying goes (as previously quoted) "brakes are meant to stop cars, not engines, which are meant to propel the car". The better technique on the track is to use the heel/toe technique to match the engine speed with the tranny... to AVOID unnecessary wear or worse: breakdown.

I have one thing to say to this stupidity. Stupidity being, (only brakes stop the car, and putting it in neutral for gas savings)

Quoting Mario Andretti, "It is amazing how many drivers, even at the Formula One Level, think that the brakes are for slowing the car down."

[Wisecraker]

I have one thing to say to this stupidity. Stupidity being, (only brakes stop the car, and putting it in neutral for gas savings)

Quoting Mario Andretti, "It is amazing how many drivers, even at the Formula One Level, think that the brakes are for slowing the car down."

Other than the stupidity thing I agree 100% with the Andretti quote. Hit the nail on the head. Using your breaks all the time to slow down, it's no good

[r4mi5awi]

I was gonna mention this 3 days ago but refrained. Now I cannot stay silent.

Somebody lock this thread already, sheesh!

You've beaten the horse's mother with this one!

[Jackal]

I was gonna mention this 3 days ago but refrained. Now I cannot stay silent.

Somebody lock this thread already, sheesh!

You've beaten the horse's mother with this one!

True dat. But I can't stop reading it.

[TheMAN]

The wear argument is very weak. You wear on the tranny/engine a lot more by engine braking, and down shifting 2 or 3 gears as you slow down, than just coasting in neutral which wears what? ... oh yeah! Nothing!

Brake pads cost much less than a clutch. So I'll use my brakes any day over my clutch to brake. I wouldn't be surprises to see the gas savings surpass the brake cost. BTW this comes from from seasoned race car drivers. On the track, the saying goes (as previously quoted) "brakes are meant to stop cars, not engines, which are meant to propel the car". The better technique on the track is to use the heel/toe technique to match the engine speed with the tranny... to AVOID unnecessary wear or worse: breakdown.

by that logic, everyone should just be using their brakes to keep their cars from going way too fast down a steep slope out west in the rockies right? if they did that, many people would've died already... truckers use their engine brakes down hills for a reason
brakes overheat when overworked, and the engine supplements the braking power by not letting the brakes work so hard... overheated brakes = no brakes.... also, if race car drivers use only brakes to slow down cars, why do they rev match down shift before a corner while on the brakes? OH because they're engine braking, duh! ever watched a race car driver driving around a road course from inside the car? I bet you haven't, that's why you're making this absurd comment

clutch and gear wear is minimal if you rev matched your down shifts, not only is there less shock load and wear on the trans related components, but there's also less shock on the motor mounts.... the gears in the trans are constant mesh, sure they do have the possibility of more wear under load, but there's negligible difference due to how the gears are assembled and the fact that gears are hardened steel... engine wear out more? are you down shifting to low gear to slow down with RPMs sky high all the time? you only do that when you need it! Otherwise in normal driving, you just keep it in whatever gear you're in (such as 5th) and just stop or slow down till you need to pick up speed again (go around a corner) and you just downshift then

[stock3]

Lots of stupid myths in this thread.

Engine braking bad - lol
Accelerating out of danger - lol
Extra clutch wear - lol

But the internet experts have spoken, so it must be true. Meanwhile millions of people drive in all sorts of different ways, like coasting in neutral, no rev. matching, clutch less shifting, downshifting for every stop etc. and have no problems with their cars.

[Wisecraker]

This is an Internet forum, where people with accounts write what they think, believe. If people want smarts go to a college or professional institution.

[geobur]

This is an Internet forum, where people with accounts write what they think, believe. If people want smarts go to a college or professional institution.

^^ this... Why is this thread still open lol? Seriously

[Wisecraker]

^^ this... Why is this thread still open lol? Seriously

Lol

[WHO]

True dat. But I can't stop reading it.

Yeah, I realize I should've stopped some time ago. I found it gunny at first and couldn't help but reply to some pretty lame/biased so-called "neutral arguments".
There's nothing neutral about discussing "ways to properly drive" as everyone thinks they know it best. Even those who use Michael Andretti as a reference, pretty much the only F1 driver who disagreed that brakes are used to brake the car... and that person failed to remind us exactly how many F1 championships that awesome, superior driver won? :P

I'm done now. Everyone, enjoy your very own way of driving your car. Some people will simply end up changing their brake pads a bit more often, while others will spend more gas or change their clutch sooner. Doesn't really matter... there are so any other factors that come into play that worrying about coasting really won't change anything.

When it comes to the OP though, I would advice against coasting in neutral with an auto tranny. That's a no-brainer and even written in the owner book.

[Booter22]

Again.. its still in the owners manual.. but hey... some one :lock this up. nothing more worth while being said here.


i would say no. i know its a big read.. but on section 5 - 13 of the owners manual ( for the 2010 ) which im sure is similar to the others, but under starting and driving about automatic transaxle controls it says:

Do not shift in to N when driving the vehicle : shifting into N while driving is dangerous. engine braking cannot be applied when decelerating which could lead to an accident or serious injury.

Caution:
Do no shift into N when driving the vehicle doing so can cause transaxle damage.