# Will placing automatic transmission in neutral while idling save gas? **URL:** \ **Category:** Factual Questions\ **Created:** [September 15, 2005, 6:34am UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743 "2005-09-15T06:34:58Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![Rhubarb](https://avatars.discourse-cdn.com/v4/letter/r/59ef9b/32.png) [@Rhubarb](https://boards.straightdope.com/u/Rhubarb)\ **Post date:** [September 15, 2005, 6:34am UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/1 "2005-09-15T06:34:58Z")
For the automotive minded: I know that the engine load decreases when I place my transmission in neutral, so I would conclude that the engine is using less gas. However, does it make any sense to shift to neutral for short periods (less than a minute or two), such as waiting at red lights? Or would any potential savings in fuel and air pollution be offset by added wear on the transmission? OTOH, would the transmission possibly benefit from spending less time under load? ---
**Author:** ![Hail\_Ants](https://avatars.discourse-cdn.com/v4/letter/h/dc4da7/32.png) [@Hail\_Ants](https://boards.straightdope.com/u/Hail_Ants)\ **Post date:** [September 15, 2005, 6:56am UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/2 "2005-09-15T06:56:38Z")
> [@](#): > > However, does it make any sense to shift to neutral for short periods (less than a minute or two), such as waiting at red lights? This could be an urban legend but believe it or not I’ve heard of there being laws against this (putting your car in neutral at a red light). The logic being that if for some reason you had to suddenly react to something you might forget to put it back into drive first… ---
**Author:** ![JerH](https://avatars.discourse-cdn.com/v4/letter/j/bb73d2/32.png) [@JerH](https://boards.straightdope.com/u/JerH)\ **Post date:** [September 15, 2005, 1:13pm UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/3 "2005-09-15T13:13:14Z")
> [@Hail Ants](#): > > This could be an urban legend but believe it or not I’ve heard of there being laws against this (putting your car in neutral at a red light). The logic being that if for some reason you had to suddenly react to something you might forget to put it back into drive first… That seems odd - honestly, I can’t imagine a circumstance where suddenly having to accelerate from a dead stop quickly would possibly be necessary. ---
**Author:** ![What\_Exit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/what_exit/32/10652_2.png) [@What\_Exit](https://boards.straightdope.com/u/What_Exit)\ **Post date:** [September 15, 2005, 1:17pm UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/4 "2005-09-15T13:17:50Z")
In theory, putting your car in Nuetral at a light would save a little gas. The Prius actually turns off to save gas at stops. As far as **Hail Ants** : I know in NJ they mentioned in Drivers Ed that it was consider unsafe by the state to coast down a hill in Nuetral but they never said anything about at a stop. Many people with Manual transmissions do both anyway. ---
**Author:** ![Balthisar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/balthisar/32/2825_2.png) [@Balthisar](https://boards.straightdope.com/u/Balthisar)\ **Post date:** [September 15, 2005, 1:52pm UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/5 "2005-09-15T13:52:57Z")
Coasting in neutral with an automatic _may_ prevent it from lubricating properly. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [September 15, 2005, 2:21pm UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/6 "2005-09-15T14:21:17Z")
Putting it in neutral takes the load (which is minimal) off the engine, but in most cars the idle speed will be higher in neutral, offsetting any savings. The difference, if any, is so picayune I doubt anyone’s even bothered to make a study of it. The transmission proper isn’t affected by this. The load is resistance to fluid flow through the torque converter, which at idle speed won’t cause any measurable wear. It’s really not worth the bother to be mindful of when to shift nor the effort to move the lever. Any time a driver has another task to do it distracts a little from his awareness of what’s going on around him, and any time a car does something unexpected – like not pulling away from a stop in good time because the driver neglected to put it back in gear – it increases the chance of meeting some other car whose driver didn’t expect it to be there. I’d say it’s more of a safety issue (small, I’ll grant) than a fuel savings issue (negligible, at best). ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [September 15, 2005, 3:20pm UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/7 "2005-09-15T15:20:09Z")
I’ll bet it costs more. Give anybody the chance to rev their engine and they always wind up revving their engine. In a real world test at the hands of the masses, too many people would rev their engines in nuetral. On paper, a tiny am’t of fuel would be saved per car, adding up to alot over time. In the real world: vroooom…vroooooooom…vroom…vroom vroom… ---
**Author:** ![Mathochist](https://avatars.discourse-cdn.com/v4/letter/m/c89c15/32.png) [@Mathochist](https://boards.straightdope.com/u/Mathochist)\ **Post date:** [September 15, 2005, 4:16pm UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/8 "2005-09-15T16:16:27Z")
> [@Philster](#): > > I’ll bet it costs more. Give anybody the chance to rev their engine and they always wind up revving their engine. In a real world test at the hands of the masses, too many people would rev their engines in nuetral. > > On paper, a tiny am’t of fuel would be saved per car, adding up to alot over time. > > In the real world: vroooom…vroooooooom…vroom…vroom vroom… Not _everybody_. As a counterexample, me. My geriatric car tends to heat up when moving slowly or stopped in gear for long periods. If I come up to what I know is a long light (getting to the light as it turns red, say) or I’m in heavy traffic that grinds to a halt, I put the transmission in neutral. I _don’t_ rev the engine. Never have, never will. What’s the point? ---
**Author:** ![mhendo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mhendo/32/3159_2.png) [@mhendo](https://boards.straightdope.com/u/mhendo)\ **Post date:** [September 15, 2005, 4:41pm UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/9 "2005-09-15T16:41:00Z")
While they don’t actually address the question of gas usage, the [Car Talk](http://www.cartalk.com/content/columns/Archive/1995/March/18.html) guys have something to say about this topic: > [@](#): > > **Ray:** I think your father’s habit dates back to the early days of the automatic transmission. When automatics were new, drivers probably didn’t trust them entirely. And there was probably some fear that these things could “run away” from you. So drivers would shift into Neutral at traffic lights because it seemed safer. > > **Tom:** But the truth is it doesn’t help the car at all, and in fact, it probably does some harm. Every time you shift to Neutral and back into Drive, you “relax” and then “stress” every component of the drive train. And all that does is wear out those moving parts. ---
**Author:** ![aerodave](https://avatars.discourse-cdn.com/v4/letter/a/f08c70/32.png) [@aerodave](https://boards.straightdope.com/u/aerodave)\ **Post date:** [September 15, 2005, 5:24pm UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/10 "2005-09-15T17:24:41Z")
> [@jrfranchi](#): > > Many people with Manual transmissions do both anyway. I sit at lights in neutral because i don’t like holding in the clutch. Also, my dad (a long time mechanic) told me it accelerated wear on the throwout bearing. But as for descending hills in neutral…that’s just dumb. Without engine compression, you will accelarate down a grade, and will be forced to keep braking to keep your speed down. Also, most modern fuel injected cars incorporate some type of deceleration fuel cutoff. The injectors are stopped when there is a reverse load on the engine. Going down a hill totally off throttle will cause the fuel consumption to go to zero. Since the wheels can keep the engine turning, it doesn’t need fuel at that time. However, if you descend in neutral, the engine no longer gets turned for free, and the car has to use a little fuel to keep the engine at idle. It’s a small amount, but more than none. So descedning in neutral only serves to waste gas and wear out brakes faster. Great idea! ---
**Author:** ![Mathochist](https://avatars.discourse-cdn.com/v4/letter/m/c89c15/32.png) [@Mathochist](https://boards.straightdope.com/u/Mathochist)\ **Post date:** [September 16, 2005, 4:43pm UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/11 "2005-09-16T16:43:44Z")
> [@mhendo](#): > > While they don’t actually address the question of gas usage, the [Car Talk](http://www.cartalk.com/content/columns/Archive/1995/March/18.html) guys have something to say about this topic: Be that as it may, cruising on my New Haven/DC trips my oil temperature sits in one range. When traffic locks up, or just crawls, it quickly climbs into another range entirely. Not quite in the danger zone, but I’m pretty sure it would get there eventually. Dropping into neutral when I’m going to be stopped for a longish period of time helps keep the temperature down. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [September 16, 2005, 4:49pm UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/12 "2005-09-16T16:49:54Z")
> [@Mathochist](#): > > Not quite in the danger zone, but I’m pretty sure it would get there eventually. Dropping into neutral when I’m going to be stopped for a longish period of time helps keep the temperature down. Your car probably has an electric fan that kicks in when the temp goes up to run air across the radiator for this very reason. Apparently it kicks in at a higher temp than you do. 🙂 ---
**Author:** ![What\_Exit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/what_exit/32/10652_2.png) [@What\_Exit](https://boards.straightdope.com/u/What_Exit)\ **Post date:** [September 16, 2005, 5:22pm UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/13 "2005-09-16T17:22:01Z")
> [@aerodave](#): > > I sit at lights in neutral because i don’t like holding in the clutch. Also, my dad (a long time mechanic) told me it accelerated wear on the throwout bearing. > > But as for descending hills in neutral…that’s just dumb. Without engine compression, you will accelarate down a grade, and will be forced to keep braking to keep your speed down. > > Also, most modern fuel injected cars incorporate some type of deceleration fuel cutoff. The injectors are stopped when there is a reverse load on the engine. Going down a hill totally off throttle will cause the fuel consumption to go to zero. Since the wheels can keep the engine turning, it doesn’t need fuel at that time. > > However, if you descend in neutral, the engine no longer gets turned for free, and the car has to use a little fuel to keep the engine at idle. It’s a small amount, but more than none. > > So descedning in neutral only serves to waste gas and wear out brakes faster. Great idea! Please don’t get the impression I do so or recommend it. I even stated (but you snipped w/o indication) that > [@](#): > > it was consider unsafe to do so. Please indicate you are taking a snip of a quote if you are going to be that negative in a response. ---
**Author:** ![aerodave](https://avatars.discourse-cdn.com/v4/letter/a/f08c70/32.png) [@aerodave](https://boards.straightdope.com/u/aerodave)\ **Post date:** [September 19, 2005, 2:02pm UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/14 "2005-09-19T14:02:40Z")
Sorry if it sounded like I was saying that you endorsed it. It was really a monologue directed at nobody in particular. I didn’t call you out. Just a bit of ranting rhetoric based in fact, that’s all. Don’t be paranoid, man 😉 ---
**Author:** ![What\_Exit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/what_exit/32/10652_2.png) [@What\_Exit](https://boards.straightdope.com/u/What_Exit)\ **Post date:** [September 19, 2005, 2:07pm UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/15 "2005-09-19T14:07:21Z")
> [@aerodave](#): > > Sorry if it sounded like I was saying that you endorsed it. It was really a monologue directed at nobody in particular. I didn’t call you out. > > Just a bit of ranting rhetoric based in fact, that’s all. Don’t be paranoid, man 😉 Its ok, I got the feeling you weren’t ranting against me 😉 It’s just good to include the …snip… so someone else glancing though doesn’t blast me, its happened before and will happen again. \*(Of course this was talking Politics or Nuclear Power not Trannies, so your comment on being paranoid strikes very true) \* 🙂 ---
**Author:** ![rayh](https://avatars.discourse-cdn.com/v4/letter/r/e79b87/32.png) [@rayh](https://boards.straightdope.com/u/rayh)\ **Post date:** [September 19, 2005, 3:26pm UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/16 "2005-09-19T15:26:07Z")
I was taught when driving that it is safer to put your car in neutral when stopped. The theory is that if someone crashes into the back of you you could take your foot of the clutch and the car would shoot forward into the back of another car or pedestrians crossing the road. Admittedly this was in a manual, but I’m sure the same argument can be made for an automatic. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [September 19, 2005, 3:46pm UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/17 "2005-09-19T15:46:54Z")
Automatics really aren’t designed engineering-wise to be continuously “manually” engaged and disengaged as part of normal driving. The Car Talk guys are right re it putting additional unecessary wear stress on the drive train. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [September 19, 2005, 4:01pm UTC](https://boards.straightdope.com/t/will-placing-automatic-transmission-in-neutral-while-idling-save-gas/321743/18 "2005-09-19T16:01:23Z")
Correction - Automatics really aren’t designed engineering-wise to be continuously “manually” engaged and disengaged as part of normal driving. The Car Talk guys are right re it putting additional unecessary wear stress on the internal transmission components