Neutral at stop lights, save gas??

[ELF]

I don't know if this has been discussed before but, I learned something today.
Until recently I never paid much attention to my GPH on the scan gauge.
So today I had it on and while at a stop light I checked to see how much fuel I was using, 0.3 GPH in gear. I put the tranny in N and the GPH changed to 0.2

So at least in my car I can save some gas by using neutral at stop lights. Don't think I'll be saving a lot but every little bit helps.

[omgwtfbyobbq]

Awesome info, I've been meaning to ask about this. Imo it means that no matter what, coasting in N should result in better mileage. I think. If you have the time, could you check the fuel flow when coasting in N compared to decelerating in gear at a kinda slow speed, like ~40mph? If the idle consumption when decelerating is greater than coasting in N, then coasting must be a win win no matter what.

[ELF]

[QUOTE=omgwtfbyobb If you have the time, could you check the fuel flow when coasting in N compared to decelerating in gear at a kinda slow speed, like ~40mph? If the idle consumption when decelerating is greater than coasting in N, then coasting must be a win win no matter what.[/QUOTE]

I checked today, hitting neutral at 40 mph....GPH was at .07 no throttle in drive.
switching to N at 40mph.. GPH went to 0.9 for about 2 seconds and then went back to .07

Seems to be no help going to neutral for coasting , at least in my car.

[LxMike]

i have found with my car that in gear coastng shows higher milage reading on my scanguage than neutral coasting.

[rh77]

Originally Posted by LxMike

i have found with my car that in gear coastng shows higher milage reading on my scanguage than neutral coasting.

My SG does the same thing, but what it doesn't know is that the injectors actually cut fuel while coasting in D (so it should read 9999).

Several vehicles benefit from Neutral idling -- the GPH arguement is quite valid. For maximum efficiency, long idling situations should be in engine-off mode (like at traditionally long lights, etc).

BUT...

The TSX, for example, has variable cam timing (i-VTEC) that cuts the cam timing dramatically at idle and uses very little fuel. It actually uses more fuel to shut-down and re-start if you're not sitting for at least 2-minutes (according to the on-board FE recorder). I don't use neutral idle anymore in the 'Teg either, as I'm worried about the longivity of the transmission going from N to D at a stop (a bit of a hard engagement). Coasting in engine-off N, starting up, and back to D with a rev-match seems to work well, tho...

RH77

[CO ZX2]

Originally Posted by rh77

My SG does the same thing, but what it doesn't know is that the injectors actually cut fuel while coasting in D (so it should read 9999).

Several vehicles benefit from Neutral idling -- the GPH arguement is quite valid. For maximum efficiency, long idling situations should be in engine-off mode (like at traditionally long lights, etc).

BUT...

The TSX, for example, has variable cam timing (i-VTEC) that cuts the cam timing dramatically at idle and uses very little fuel. It actually uses more fuel to shut-down and re-start if you're not sitting for at least 2-minutes (according to the on-board FE recorder). I don't use neutral idle anymore in the 'Teg either, as I'm worried about the longivity of the transmission going from N to D at a stop (a bit of a hard engagement). Coasting in engine-off N, starting up, and back to D with a rev-match seems to work well, tho...

RH77

It doesn't appear to me that you guys are differentiating well between coasting with engine on and engine off. When you are coasting with engine off NO fuel is being consumed. So how can your fuel consumption be less than that? Coasting in gear only slows your car down faster, how can that be good? If there was total fuel cut at any time with any car, the engine would die. Engine Off Coasting is a sure fire way to substantially raise your FE. It worked for me and has worked for many others.

[GasSavers_Ryland]

Originally Posted by CO ZX2

It doesn't appear to me that you guys are differentiating well between coasting with engine on and engine off. When you are coasting with engine off NO fuel is being consumed. So how can your fuel consumption be less than that? Coasting in gear only slows your car down faster, how can that be good? If there was total fuel cut at any time with any car, the engine would die. Engine Off Coasting is a sure fire way to substantially raise your FE. It worked for me and has worked for many others.

If your engine runs extreamly rich on start-up, then to restart your engine can use more fuel, then if you had let it sit there idleing if it would only have been idleing for a few seconds.

[BeeUU]

I have noticed that on my newer car (2002 Mazda Mpv with auto trans) when I lift the transmission disengages and the engine falls to idle. When I hit the throttle the trans reengages. The MPV is a ULEV and to keep the converters at temperature the exhaust gas has to be hot. So no fuel cut while coasting. This is my guess......

So FE is sacrificed for emissions in this case. Pllus it makes for some nasty bumps from the driveline while driving in traffic, not so good.

[Peakster]

Originally Posted by LxMike

i have found with my car that in gear coastng shows higher milage reading on my scanguage than neutral coasting.

Same with my dad's Chrysler. It depends on the car whether its sensitive to being in gear or not.

[budomove]

According to Ben (SVOboy) the fuel injectors on hondas turn off while coasting in gear, so the same goes for us.