Putting a car in neutral saves gas?

I’ve been told that putting a car in neutral while it is stopped saves gasoline. Does it really? If so, is it worth doing for what seems to be a very small amount of gas?

IANAmechanic, but if there’s any truth to Arnie’s claim, it would only be in the case of automatics. In manual transmission cars, you will not save any fuel, even theoretically.

I’m not really clear what Arnie’s saying, because if you shift an auto from drive to neutral, the engine will idle a little higher, because it’s no longer under the strain of tensioning the drive train.

So I don’t think there’s any saving in any kind of car. And if there is, it’s infinitesimal. And Arnie correctly points out one of the hazards of shifting to neutral at a stop.

Don’t do it.

Putting a (manual) car in neutral won’t really save you much gas, but your clutch will survive much longer if you put it in neutral when you’re stopped.

IANA mechanic, but my dad is.

Depends on the car. On older cars, the idle is simply a set screw on the carb. Doesn’t make any difference if you’re in drive or nuetral, the same amount of gas is going to be flowing.

On a newer car, if the computer controls the idle speed, then the computer may adjust the consumption of gasoline down a bit if you put it in nuetral to get the idle down to what it thinks is the proper rpm for idling. The extra load for the torque converter while in drive will make the computer use a bit more gas to adjust the idle speed.

I think most of the energy just goes into sloshing around the fluid in the torque converter, which I suppose does eventually get converted into heat.

In addition to the already noted lack of an appreciable savings in gasoline consumption, I’ll toss in the perspective shared by many of my former fellow taxicab owners: there’s a finite number of shifts in the life of every transmission.

I’m not sure what the definition of a “newer” car is…This one is an '89. But I suspect that Ringo is right, so no more neutral-ing.

Can anyone confirm or deny this asertion? My rather meager understanding of a Manual transmission is that when the clutch is in, there is no true mechanical connection between the engine and the transmission, the flywheel spins, the pressure plate does not. If this is true, why would it matter what gear (or neutral position) the transmission is in?

Now if Sqube meant that the transmission should be in neutral, but your foot not on the clutch…which means the flywheel and pressure plate are engaged, so the input shaft of the tranny is turning, but it is connected to none of the gears, therefore, just the “front” of the gearbox is spinning.

So, how is that possibly better than leaving the clutch depressed?? The only “Wear and Tear” I can imagine leaving the clutch depressed is on the springs/cables/hydraulic system/whatever that actuates the clutch.

Were I to guess, I would imagine the best thing to do at a stop-light is to keep the clutch depressed, and that it madde no difference what gear the transmission is in.

I usually just kept my car in 1st, with the clutch down. Is this worse, and if so, how?

Steve

It’s not the clutch plates that wear prematurely when you keep the clutch disengaged at stops - it’s the clutch throwout bearing. This part goes between the moving clutch plate and the stationary clutch linkage, and wears only when the clutch pedal is depressed. In normal driving, the wear only occurs during the short time you are actually shifting. If you sit for minutes at a time with the clutch disengaged, the wear on the clutch throwout bearing increases greatly.

Ahh, I see…yeah, that makes sense then. Didn’t think about the throwout bearing (You’d think I would since I’ve replaced one, but, alas, didn’t occurr to me sitting at the PC)

Thanks, Jeff!

Steve

Although it is an often quoted “rule”, and I often repeat it myself, I am actually unaware of any scientific/statistical study that shows on modern automobiles whether or not release bearing failures are prevented or delayed by holding the clutch less. One would think it would have an effect, but…?

Drivers of automatics:

Whether or not it saves you fuel, I’d prefer it if you put your car in neutral (and engaged the handbrake if on a slope) rather than sit on your footbrake dazzling the guy behind you (i.e. me) with your brakelights.

Automatics are a bit different than manuals in how they transfer energy. A manual uses a direct, mechanical connection that can be disengaged when stopped so that the engine can spin freely, or n change gears.

An automatic uses a system with two rotors, in a chamber filled with fluid. One rotor is connected to the engine, the other connected to the transmission and driveshaft. When the engine’s rotor turns, the fluid begins to move, and propels the other rotor. The liquid is at a viscosity that allows it to fairly effeciently transfer engine power, but also spin freely while the car is not moving. Because some slippage is necesary, the automatic is not as effecient from either a perspective of gas mileage or acceleration.

Many newer automatics have a “lockup torque converter” which is basically a conventional manual transmission clutch that connects at a certain speed to bring manual-like mileage on the highway.

But to get back to the point, when in Neutral, the drivetrain side rotor is spinning freely, decreasing the load on the engine. Therefore, yes you’ll save gas… but probably not enough to matter unless you are stopped in traffic for hours, in which case you should turn the engine off.

Do you really expect people to use the parking brake while stopped at a stoplight?

I can’t believe you find brake lights dazzling!

I also shift to neutral (and apply the footbrake) for no other reason that it relieves stress from my leg. Why sit there with your car in gear and your foot on the clutch pedal?

Here’s one more reason not to neutral(ize): If it’s a long red light, I may forget that I’m in neutral. Ever tried accelerating that way? oops!

Thank you, all who have responded. This is turning into quite the lesson.

Actually…as long as we’re at it, and since I feel perfectly justified in 'jacking my own threads…

I’ve only had this car since spring 2001, and only three times since then I’ve had a temporary yet scary situation: I pull a lever to get the headlights on–or, more specifically, to flip up the panels over the headlights so that they can be seen. 99% of the time they flip up. But three times they have not, and I’ve had to drive home at night with no lights in front.
Any guesses here? I’m figuring it’s an electrical problem of some kind.

Can I buy a vowel here? You said earlier that the car in question is an 89, but how about a make and model.

Well, considering every component involved here is part of the electrical system, an electrical problem is probably a safe bet.

:smiley:

Do other lights come on when you turn on the light switch and this happens (i.e. the dash lights, rear lights, etc)? If not then the problem is in the switch itself.

Most cars that I’m familiar with that have flip-up headlights have an individual motor for each light. But then I’m not a mechanic so I don’t see a whole lot of cars. If a motor is going goofy, then you end up with a winker (one headlight up and the other down, like the car is winking at you). The odds of losing both motors simultaneously are so low as to be about zero, so the motors are probably ok. However, you might have a spotty ground connection where both motors connect to ground.

Since I don’t know what kind of car you have or how the headlights are wired, I can only guess that there is probably some sort of relay that drives them to open up. Possibly this relay has started to go bad.

Well, the lights work, but I thought maybe the panels were just “sticking” for some reason and maybe it wasn’t electrical at all. Can’t really tell, but I don’t see any way to force them up manually. All the other lights come on just fine.

This is an '89 Dodge Daytona CS Turbo. It could very well be something that is just getting worn out from age.

Not sure on a Dodge Daytona, but on a Porsche 924 the barn door headlights are both raised by one motor. There is a bar along the front of the engine bay that connects the two lights. Twisting this bar allows the lights to go up or down. Had to do this when the motor went out on a Porsche.

As for the manual tranny I always go to neutral and let the clutch out. Not really for any mechanical reason, it is just tiring to hold the clutch in for that long.