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-   -   Shifting To Neutral At Red Lights...Saves Gas?! (https://www.fuelly.com/forums/f33/shifting-to-neutral-at-red-lights-saves-gas-9596.html)

ben89 08-01-2008 03:43 PM

Shifting To Neutral At Red Lights...Saves Gas?!
 
I've heard that it's possible to save a bit of gas by shifting to neutral when you're at a red light. Has anyone else heard such a thing?

theholycow 08-01-2008 03:54 PM

With an automatic, it helps slightly. The saving is very slight, as is the effort.

GasSavers_RoadWarrior 08-01-2008 04:04 PM

Apparently some transmissions still run full pressure though the torque convertor while in neutral, and have the clutches disengaged while your foot is on the brake so savings are slight. Whereas when they are in park lubrication pressure is reduced and the pump is not working as hard. Full lube pressure at neutral is probably good for neutral coasting, but likely won't save you as much at stop lights as putting it in park would. However, if you've been slogging uphill recently at low city speeds and have been surfing the torque convertor, you might be better off leaving it in neutral as the higher lube pressure should give better cooling of the transmission through the tranny cooler.

azraelswrd 08-01-2008 05:22 PM

It saves a tiny bit. From my scangauge, if I'm in idle-D I can use from 0.20 to 0.22 gallons per hour. If am in idle-N, I go down to 0.14 to 0.17 gph and remember that this lasts for all of 5 to 7 seconds while waiting at a light so don't expect the world in savings. But it's zero effort for minimal gain, so why not? :)

(turning the engine off for a long light/wait [more than 10 sec] is the better recourse)

collegekid01 08-01-2008 05:48 PM

lol and it's like a strange safety measure too because it's a pain to do while your on the phone, I end up cutting my driving calls short cuz of it

swng 08-01-2008 06:01 PM

I have done that before and noticed that the rpm did drop a little bit whilst in N. I take it to mean saving of a little bit of gas.
When I shift to N at a red light, I leave my hand on the shift knob to remind myself to shift back to D when it is time to go.

Jay2TheRescue 08-01-2008 06:16 PM

I've gotten mild RPM drops and fuel rate drops as reported by ScanGauge in my truck by shifting into N at lights. Every little bit helps. Today I figured out DFCO, and will use that in conjunction with my stoplight strategy in hopes of raising my city mileage in The Beast even more. Currently I'm getting about 14 - 15 MPG city in a truck EPA rated (new ratings) for 12 city.

-Jay

1cheap1 08-01-2008 10:48 PM

If you do it right you are in neutral as you coast up to the light. I Do this with both automatic cars that i have.

Jay2TheRescue 08-02-2008 05:02 AM

Neutral coasting to the light is better than race to the light and slam on the brakes, but wouldn't DFCO be better if your vehicle is capable?

Project84 08-02-2008 05:48 AM

In my saturn, at a red light IN GEAR the gallons per hour is reading .45

when I slip it into neutral that drops to .32

So basically, in gear at a red light, I could sit there 2 hours and burn one gallon of fuel.

In neutral it would take 3 hours.

theholycow 08-02-2008 09:28 AM

Quote:

Originally Posted by Jay2TheRescue (Post 113672)
Neutral coasting to the light is better than race to the light and slam on the brakes, but wouldn't DFCO be better if your vehicle is capable?

Most of the time, yes, in my experience. If you could neutral coast to the light and not have to brake at all then it would be better than DFCO, but that requires you to be really good at predicting when the light will turn.

thisisntjared 08-02-2008 05:49 PM

Quote:

Originally Posted by collegekid01 (Post 113617)
lol and it's like a strange safety measure too because it's a pain to do while your on the phone, I end up cutting my driving calls short cuz of it

your talking on the phone while you are driving??
Quote:

Originally Posted by Project84 (Post 113674)
In my saturn, at a red light IN GEAR the gallons per hour is reading .45

when I slip it into neutral that drops to .32

So basically, in gear at a red light, I could sit there 2 hours and burn one gallon of fuel.

In neutral it would take 3 hours.

so if one spends an hour total a week(10min a day on weekdays plus 5min a day on weekends) idling at traffic lights, assuming $4/gal, thats almost$2 in gas if you have it in gear and $1.33 if its in neutral, a savings of less than $.70.

keep in mind your average traffic light is between 1 and 3 minutes and since one often doesnt spend the full time at the traffic light, for my calculation i did 1 minute per light.

now a lot does depend on ones commute, but if one fills up once a month and drives in traffic like i do, thats $2.80 in savings for each fillup, which is .7 gallons. i know i drive a manual, but hypothetically if i were to have an auto and it would behave like your saturn and all else was equal and i left it in gear, i would be getting approximately 2 less mpg, assuming i fill up at 300miles and currently average 30mpg making the fill up 10gallons. wow that is one massive run on sentence that i dont feel like fixing.

going from 30 to 28mpg would suck!
Quote:

Originally Posted by theholycow (Post 113696)
...but that requires you to be really good at predicting when the light will turn.

if there is not a left hand turning lane for opposing traffic, then it is 3 seconds after when the traffic light before yours turns from yellow to red. of course you have to know the intersection, but if you do screw up and put the car in gear, bfd, you still havent gone anywhere because your foot could still be on the brake.

Jay2TheRescue 08-02-2008 05:52 PM

Get a bluetooth headset...

theholycow 08-03-2008 03:55 AM

Quote:

Originally Posted by thisisntjared (Post 113746)
if there is not a left hand turning lane for opposing traffic, then it is 3 seconds after when the traffic light before yours turns from yellow to red. of course you have to know the intersection, but if you do screw up and put the car in gear, bfd, you still havent gone anywhere because your foot could still be on the brake.

I was talking about approaching stale red lights in neutral or in gear so you won't have to stop at all; and the issue is that you can't see the other lights.

GasSavers_GasUser 08-03-2008 07:10 AM

FWIW it might depend on the vehicle/tranny. I tried it with my jeep and get the exact same GPH reading on the scangague wheather I am in N or D at the stoplight. No difference.

So, my driving boils down to ......If I want fun, I drive the jeep. If I want gas mileage, I drive the car.

The thing is, when I "turn on" the jeep, it returns the favor.......the car - not so much.

Just my experience.

thisisntjared 08-03-2008 01:33 PM

Quote:

Originally Posted by theholycow (Post 113777)
I was talking about approaching stale red lights in neutral or in gear so you won't have to stop at all; and the issue is that you can't see the other lights.

oh right! haha my bad for taking it out of context

ziddey 08-03-2008 05:39 PM

Depending on the car, you may be able to adjust the idle off spec. I have a vw fox and I've unplugged the idle boost valve so it won't try to keep the idle at 900rpm. Then I've adjusted the idle speed screw and air fuel mixture screw. Now my idle is around 500-800. It's not consistent though which is strange since I don't have the boost valve anymore.

That said, not all cars can maintain a low idle without being incredibly lumpy or stalling out. A problem I also have with my car is that if the idle is set low, initial throttle response is absolutely poor, and it hesitates for a second before revving up. There's an ecu piggyback for my car that addresses this, and I'll probably get that, although it's completely irrelevant to your case. (Sorry to post junk!)

Perhaps if you were able to lower the idle lots, it'd help a bit more, although again the differences would still be slight and you probably wouldn't see more than 0.1mpg if that. Unless of course you're driving in bumper to bumper nyc traffic

palemelanesian 08-04-2008 08:31 AM

My odyssey V6 reads 0.5 gph idling in Drive, and 0.45 gph in Neutral. Small but repeatable improvement.


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