Does it help to put it to neutral when preparing to stop?

[Lord Northern]

Hey. I own a Subaru Impreza 2001 automatic and I was wondering:
My dad keeps telling me that if you see the red light from far away or if you know you're going to slow down to turn, you should put it to Neutral.
That way, the engine doesn't push the car forward and it saves fuel.
Some other people told me that simply not pressing the gas pedal does the same effect since if gas is not pressed, it's not pushing the car forward anyway and spends the same amount of fuel as if it was on Neutral.

Thanks in advance.

[sickcallawayc12]

Putting it in neutral saves gas. That's pretty much it. Not really a safe thing to do all the time. I say don't bother unless you are on a long trip and you want to maximixe your fuel economy.

[beef_bourito]

it will waste gas

when you're in gear and coasting to a stop (foot off the gas) the engine doesn't need to inject fuel. if you stick it in neutral it has to inject enough fuel to stay at idle. so in gear = no fuel injected, neutral = a bit of fuel injected. either way you won't be saving or wasting alot of fuel but if you've got an automatic you'll be wearing out the tranny alot more by switching in and out of neutral.

[dave92cherokee]

Originally Posted by Lord Northern

Some other people told me that simply not pressing the gas pedal does the same effect since if gas is not pressed, it's not pushing the car forward anyway and spends the same amount of fuel as if it was on Neutral.

If the vehicle is in any drive gear or reverse and you put on the brakes it will still try to move the vehicle forward but the friction of the brakes stops that. And to prove it try putting it in drive or reverse and not touch the gas or brake and it will move just slower. As far as neutral not injecting fuel and drive injecting fuel what do you think actually keeps the car running? If it's in neutral usually the engine rpm's are a little higher than when sitting stopped with the brake on so neutral in some aspects would use more gas. Only time it will be a big advantage is when you're on a long trip and trying to conserve every gallon of fuel possible to make it last longer. But it will also accelerate the wear on your tranny as said since an automatic isn't designed to be driven that way.

[J-Ri]

Originally Posted by beef_bourito

it will waste gas

when you're in gear and coasting to a stop (foot off the gas) the engine doesn't need to inject fuel. if you stick it in neutral it has to inject enough fuel to stay at idle. so in gear = no fuel injected, neutral = a bit of fuel injected. either way you won't be saving or wasting alot of fuel but if you've got an automatic you'll be wearing out the tranny alot more by switching in and out of neutral.

Agreed, mostly. In gear and coasting you still use fuel, just not as much. If you have access to a scan tool with datastream capability, watch the injector pulse width under all conditions. On my car, I use about 1/2 the fuel leaving it in gear and coasting as opposed to shifting to neutral. Your dad was right... back in carbureted days, but it's not true with fuel injected vehicles. Here in Iowa it's illegal to coast in neutral... but I don't know how they could possibly inforce that.

If you have a manual transmission, you can put it in 5th gear and turn the ignition switch to "unlock" and save quite a bit of gas if you drive down a 3/4 mile hill every day. That way you still have power steering and vacuum to refill the brake booster.

About the idle RPM in gear and in neutral... fuel used is very close to the same. Even though the RPM is higher in neutral, the engine load is less. I would expect fuel used to be nearly identical.

[ahoier]

Something I noticed, when switching to neutral at a long light, when I switch back to Drive (automatic transmission), I get quite of a "jump start" (like, quick acceleration) when I tap the gas. Whereas, normally my Rio is slow to accelerated (4 cylinder). But switching to Neutral when stopped, I notice this "pep start" when I switch to Drive.


So, perhaps gas is still being "used" while in Neutral?

But since It's not in "drive" (and my foot on the brake petal) - the car isn't trying to move itself, so it "saves up" the gasoline/pressure to give that peppy startup when I tap the gas?

lol, it's weird, but it makes sense anyways :P

[dlbitron]

Neutral coasting is ILLEGAL in most states just so you know... not that anyone would find out until you cause an accident. Don't do it. If your car is running you're using fuel. You can save some fuel by not turning off your car for small things like running into your house for your wallet or something, leave your car on, idling for 20 minutes uses the same fuel it costs to START your engine once. I'd say shift at a natural RPM, depending on your motor, i have a 4cyl 2.0 and I shift at or up to 3k rpm and keep it at 2k rpm (when i'm low on fuel), over revving your engine uses more fuel than you think.