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.

[LxMike]

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

[omgwtfbyobbq]

Really? That's very interesting. Do you know if fuel is being injected or not? For example, on the Camry, depending on coolant temps, when I coast (in gear) and drop below ~1200-1500rpm fuel starts being injected, and it pretty much idles down the road in gear. But if I'm coasting (in gear) above those rpm in top gear (greater than 50mph), no fuel will be injected. I'm wondering if the fuel flow for in gear idling is the same as N idling...

[LxMike]

I'll have to check gph readings and see.

[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

[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.

[repete86]

Do you know if this applies to all Hondas? I generally drop into neutral for short coasts and turn the engine off for longer coasts because when I eave it in gear it slows down considerably faster and I know that when I'm stopped that going into N will save gas. I would just experiment, but I don't drive very often except when I'm on a job, so for me to go from tank to tank would be difficult, and I don't have a SuperMID.

[GasSavers_Bruce]

Using liters instead of gallons on the SGII will give better resolution of the idle fuel consumption. I found that my idle fuel consumption at a stop went down about .1l/h in neutral. One gallon = 3.785l. Watch for any transitional changes that may eat up any gains over a short time out of gear.

If you do a lot of ICE-off coasting, changing the SGII engine type to "hybrid" and keeping the key in the "run" position as much as possible should give the trip mileage better accuracy.

GPH Fuel consumption in my car is about the same coasting in neutral or drive, but above 30 MPH it slows down faster in drive because of engine braking. MPH/GPH = MPG, so the faster you're going during ICE-on coasting, the better the gas mileage. ICE-on coastdowns in neutral at high speeds will give better gas mileage in my car because it remains at high speed longer.