After learning that the NEW fuel injectors "turn off" when coasting in gear, but not when coasting out of gear, I tried it. Sure enough there's a mileage increase shown on the DIC that is greater coasting in gear.

What is really noticeable, is the improvement you get by making sure to get your right foot completely off the gas pedal any time there is a chance to coast and then by taking it easy as you resume speed.

old news. car manufacturers have been doing this for years. its called Deceleration Fuel Cut Off (DFCO)
you can mess with it in hptuners

Indeed, it's something that has been done for years, but nonetheless, most people don't have the patience to cost up to a red light these days. :lol:

its just as easy and almost as good to downshift and creat such a huge vacuum that it gains milage

if your coasting in gear that can't be good for your throwout bearing

if your coasting in gear that can't be good for your throwout bearing

its fine, you arn't supposed to coast out of gear for safety reasons anyway

if your coasting in gear that can't be good for your throwout bearing

Haven't had one for years....

hmmm, interesting.

if your coasting in gear that can't be good for your throwout bearing

huh....the throw out bearing goes bad when you sit on the clutch for ever....adn coast that way....coasting in gear doesnt harm a single thing...

It's how I drive (usually). I averaged 28mpg on my last tank of gas, all city stop and go driving. Not too shabby eh? Considering the car is only rated at 22mpg city ;)

huh....the throw out bearing goes bad when you sit on the clutch for ever....adn coast that way....coasting in gear doesnt harm a single thing...

Only thing it harms is the oil companies pockets becuase you are using less fuel.. rofl

ive been tryin to tell neutral coasters this for years on this board.
im glad a few people are finally figuring it out lol.

ive been tryin to tell neutral coasters this for years on this board.
im glad a few people are finally figuring it out lol.

I've been driving every MT car this way. Shit I even do the same with my riding mower when I need to slow down. lmao :lol:

I've been driving every MT car this way. Shit I even do the same with my riding mower when I need to slow down. lmao :lol:

lol yeah. some people get it.
but theres a scary number of people out there who ride around in neutral.

where can i find these at ?

lol yeah. some people get it.
but theres a scary number of people out there who ride around in neutral.

Oh I know it, I feel like slapping them sideways when they tell me they do it to "save gas." :cussing:

Some people think the higher the RPMS, the more gas you are using. That's probably why they do it.

What is really noticeable, is the improvement you get by making sure to get your right foot completely off the gas pedal any time there is a chance to coast and then by taking it easy as you resume speed.


people need to really take note of this point too, its very important.
when your on any kind of downslope at all,
if your in 5th, you will find that you often wont slow down at all if you let off completely,
but by keeping a tiny bit of throttle, or being in cruise, you use more fuel than getting off the peddle and letting it go into DFCO.

helps mileage ALOT over the course of a long trip.

good job. it's nice to see that there are people willing to learn on the site. so many people are too stubborn, and think they know everything. keep doing it, and you'll be saving a decent chunk of change.

I had a big argument about this on here a while ago where I tried to explain the DFCO theory.. I got shot down and people told me I was wrong. Where are those people now?

probably driving a rusted out 200000 mile 94 civic, because their rammed their cobalt up someones ass at a stop sign :D

probably driving a rusted out 200000 mile 94 civic, because their rammed their cobalt up someones ass at a stop sign :D

rofl

If you happen to pay attention the next time your in your car for all of the non believers, check your idle when you are sitting in your drive way before you head out. Once your down the road put the car in nuetral and notice that your rpms are most definetly higher than when you are sitting still.

it actually doesnt matter what RPMS its at in neutral.
because when your in neutral, your engine is using fuel to idle at whatever rpm
but when your in DFCO, your using NO fuel.

any fuel > no fuel

:D

I realize that I was just suggesting that it does in fact use more fuel in nuetral at speed vs standing still

I had a big argument about this on here a while ago where I tried to explain the DFCO theory.. I got shot down and people told me I was wrong. Where are those people now?


I absolutely hate how people will do that to someone else, but most of the time its because it happened to them. I barely participate in many forums now because of that exact reason.

I had no clue about this DFCO AT ALL. So reading this post has informed me of something new, its like gas just dropped a dollar a gallon now that I read this. Thanks a lot to the OP for bringing it up, and to the rest that confirmed.

i'm assuming the coasting in gear also includes braking in gear as for using no fuel?

yes. as long as dfco is enabled.

I'm about 2 years behind I'm sure, but it looks like the DFCO blips the injectors at around 1300 RPM to keep the engine going (and if you drop below 1k, at least from what I've experienced, the SS S/C brings on some boost to keep the engine from dying, not sure what happens on the N/A cobalts). Cruise control would prevent DFCO from ever happening methinks, but correct me if I'm wrong.

Very nice if you're traveling at 65 MPH and see a downhill coming. Tried it this morning, very impressed, beat my cruise control average MPG's down the hill near my house by a few ticks.

Seems like DFCO > Cruise Control > Neutral Coasting, good stuff.

your correct on both counts.
DFCO will not engage with cruise on,
and you also want to keep your rpms above 1500 (just downshift :D)

There are a couple of cars out there that have the fuel cutoff turned off from the factory. The Z06 for example won't cut off fuel while coasting in gear on the stock tune, since the fuel cut off is turned off from the factory. You can turn it back on with a tune though.

can causing a vacuum save gas?

The ONLY thing is...you put more wear on the crank

:lol:

Which if someone wears out a crank...call me so you can hear me lol at you.:lol:

The ONLY thing is...you put more wear on the crank

:lol:

Which if someone wears out a crank...call me so you can hear me lol at you.:lol:

I wore out my crank with my massive Stage 2 Horsepowerz :cssNET:

There is alot of info in here that I did not know. Thank you'll for sharing. This should help me out alot. I never really took the time to come into this forum. Im glad that I did because I never coast in gear. I usually coast out of gear. Now i know its not safe but I dont do it that much.

well other than using more gas, coasting out of gear also does not allow you to respond as rapidly in and emergancy.

if your coasting in gear that can't be good for your throwout bearing

The throwout bearing is only used when you use the clutch..when your foot is completely of the clutch petal there is no strain on the throwout bearing.

I am all up for saving fuel, with gas prices the way they are.. I plan on using this method... I can see this working with both auto's and manuals.. just coast down a hill, and/or coast up to stop lights... The only adverse effects could be slightly more engine wear..like on the crank bearings, rings and valve train... but I dont think it would in anyway cause a major effect on the life span, by no means...

How come when I coast through my neighborhood in neutral I can instantly see my gas mileage go up?

*facepalm*

isnt it where when you have it in neutral coming to a light instead of downshifting you waste gas because its just free floating rpm, instead of controlled like when you downshift?

*facepalm*

I know I get better mileage when Im in gear, I never neutral coast on the road, Im just curious cause it doesnt seem to make sense if my DFCO enables at 1800 and disables at 1600 but I get better mileage coasting in neutral to my house

ill explain this once more, for those that didnt read the thread.

Neutral coasting is the equivalent of idling your vehicle, while you roll.
IE fuel is being used to idle the engine.

DFCO, is when you coast IN GEAR, but the engine does not need any fuel to idle, as it uses the momentum of the car, to keep the engine rotating, WITHOUT using any fuel.

beside the fact that neutral coasting is unsafe, and one of the stupidest habits drivers have,
it uses MORE fuel, than downshifting like your SUPPOSED to do.

(king, try downshifting to the appropriate gear so your above 1800rpm while coasting in gear,
P.S neutral coasting in a residential is probably the worst place to do it. your vehicle control and braking distance are not nearly as good, and thats usually when a kid scoots out on the road in front of you, please dont do it)

ill explain this once more, for those that didnt read the thread.

Neutral coasting is the equivalent of idling your vehicle, while you roll.
IE fuel is being used to idle the engine.

DFCO, is when you coast IN GEAR, but the engine does not need any fuel to idle, as it uses the momentum of the car, to keep the engine rotating, WITHOUT using any fuel.

beside the fact that neutral coasting is unsafe, and one of the stupidest habits drivers have,
it uses MORE fuel, than downshifting like your SUPPOSED to do.

Then why am I seeing an increase in mileage when I neutral coast?.. I read and understood all of this, Im not dumb, its a very basic and simple concept to understand.

of course you will see an increase when you neutral coast.
but you will see MORE of an increase, when you use DFCO

It goes up because you are not pushing the gas pedal silly. Now if you left it in gear though...it saves a LOT more gas.

of course you will see an increase when you neutral coast.
but you will see MORE of an increase, when you use DFCO

damnt just beat me.:lol:

of course you will see an increase when you neutral coast.
but you will see MORE of an increase, when you use DFCO

I see a decrease when Im in gear in my neighborhood though, and Im normally around 2200 which means my DFCO is engaged and Im not on the peddle, this is why Im confused..

if your coasting down in gear at 2200rpm, and not seeing a boost in mileage, something is off....

you dont have an auto do you?

nah, 5 speed. Its normally about a .1-.3 increase when I take it out of gear

do you have a custom tune?
what model of car are we talkin here?

Custom tune on a 2.4

bingo.

gotta go to work. ill dig into this more with you tommorow if you like.
but i can almost garuntee its the tune.

For what it's worth, I've noticed that in my car, DFCO only appears to activate in 5th, and cuts off when the car goes below 1250 rpm. I've taken it up to 60 in 4th and just let off the gas, and if it were cutting fuel 100%, the instant readout would peg at 99mpg right away. Only does this in 5th.

bingo.

gotta go to work. ill dig into this more with you tommorow if you like.
but i can almost garuntee its the tune.

Word, maybe I can get you a copy of a log or something and you can see what you can do. You seem to be pretty good at getting awesome mileage in these cars

For what it's worth, I've noticed that in my car, DFCO only appears to activate in 5th, and cuts off when the car goes below 1250 rpm. I've taken it up to 60 in 4th and just let off the gas, and if it were cutting fuel 100%, the instant readout would peg at 99mpg right away. Only does this in 5th.

hmmm thats rather interesting too.
im assuming your on a custom tune as well?

Word, maybe I can get you a copy of a log or something and you can see what you can do. You seem to be pretty good at getting awesome mileage in these cars


whos tune are you running?
its pretty common for people to turn off DFCO during tuning, so its quite likely they may just have forgotten to re-enable the engagement qualifiers.

The DFCO is much more apparent if you have a wideband AFR gauge to monitor...

Idling or cruising very slightly on the gas my LC-1 w/ DB-Red reads around the 14.7 range... If I am fully off the gas and coasting in gear, it will read 22.4 (or some gauges read "lean" or "error" as they don't go that lean). This is also the reading the gauge gets when the O2 sensor is completely in open air. Soo this is accurate, the exhaust is ALL air, NO gas...

DFCO is real and it does work. If it isn't working, and your tuned, it was probably turned off...

hmmm thats rather interesting too.
im assuming your on a custom tune as well?

Stock 2008 ss

Never watched it on the old car, since it didn't have the instant readout, but it's pretty easy to notice when you have the DIC telling you your instantaneous mileage.

DFCO is proven to be better with a MT then a AUTO but my question is in a auto will DFCO be better then in natural?

SS/TC's as well?

For what it's worth, I've noticed that in my car, DFCO only appears to activate in 5th, and cuts off when the car goes below 1250 rpm. I've taken it up to 60 in 4th and just let off the gas, and if it were cutting fuel 100%, the instant readout would peg at 99mpg right away. Only does this in 5th.

Yeah, I've noticed similar, sort of. It seems as though the DFCO on my SS/TC (08) kicks in when coming from above 2750 and through roughly 2250 (if I'm remembering correctly), judging by the INST on the DIC. Downshift and have revs below 2750, your not at 99. Let it fall below 2250 on the coast, and it drops from 99.

I don't know if that's the way it is designed or what, but that's what I've noticed.

Oh, and yes, that's not in fifth. Fifth seems to be 99 on a coast.

Yeah, I've noticed similar, sort of. It seems as though the DFCO on my SS/TC (08) kicks in when coming from above 2750 and through roughly 2250 (if I'm remembering correctly), judging by the INST on the DIC. Downshift and have revs below 2750, your not at 99. Let it fall below 2250 on the coast, and it drops from 99.

I don't know if that's the way it is designed or what, but that's what I've noticed.

Oh, and yes, that's not in fifth. Fifth seems to be 99 on a coast.

after you go below a certain rpm, the injectors kick back on. i'm not sure what it is, in my car it doesn't seem to matter what gear i'm in, but somewhere right below 18mph you can feel the injectors come back to life.

i wonder how much gas you use when you downshift instead of putting it in neutral to stop
I would imagine giving the pedal a "blip" of gas for each gear would amount to more than the idle amount

try it and see.
ive tested it countless times, but no one will believe me anyway :D

i wonder how much gas you use when you downshift instead of putting it in neutral to stop
I would imagine giving the pedal a "blip" of gas for each gear would amount to more than the idle amount

when you downshift you're using ZERO gas. the fraction of a second blip is nothing, all you're doing is raising the rpms a little bit in neutral.

Has anyone here gone to standard transmission driving school? Yeesh!

Downshift to slow yourself down over a long coast or going down a hill.

Saves gas.

Saves brakes.

Saves lives.

What is there to argue about. Forget what phantom "improvement" you may think you get doing something. People drive manuals this way for a reason. GET OVER IT.

prepare to be frustrated lol.
we have been saying this stuff for years, the kids still think neutral coasting is ftw, and rarely listen.