I was reading this page on tips to save gas, and #8 states that putting the car into neutral while idling for long amounts of time puts less strain on the transmission. Would putting the car into Neutral during long periods of idling (such as being stuck in a traffic jam, etc.) really save gas? If so, is it a lot? of gas saved? Thanks. 
Sure it saves gas your engine works harder straining against the brakes. I go into neutral a lot just to save engine wear because your tends to overheat in traffic anyway.
But would the savings in gas make up for the extra wear and tear on the clutch everytime you shift from Drive to Neutral during idling? 
How much more wear and tear on the transmission can one expect if they do shift from Drive to Neutral each time they are stuck in traffic idling?
Does your car’s engine work harder when in gear? Well yes, but not but a bunch. Will you save gas by putting the car into neutral? Again yes, but the amount is so small I doubt you could detect it with the with your fuel gauge (which is not exactly a precision instrument)
Will taking my car out of gear, make my trans last longer? I doubt it. In fact I think I could make an argument that taking it in and out of gear would accelerate the wear on the clutches.
henrijohns this is not a good reason to take your transmission out of gear at a light. It is however an excellent reason to get your overheating fixed before you severely (and expensively) damage the engine. Lots of cars out there have aluminum cylinder blocks and heads, and they DO NOT like to be overheated. Stuff that 30 years ago would have been no big deal, now could destroy an engine. Your car, your call, but if you don’t get it repaired, don’t come whinnying if the engine blows.
Put it on neutral if you are waiting for a drawbridge or at someone’s door. Then again, you might consider turning off the engine on those situations. Then again, again, hot summer, children in the car, A/C. Neutral it is.
It seems to me that having it in neutral would use more gas. Sure, having it in gear puts a slight load on the engine, but you’re not opening the throttle to match it. The engine has the same restriction in the intake, but is turning more slowly. That means less air and thus less fuel. Am I missing something?
Depends on the car. For an older car, the idle is set by a screw on the side of the carburetor and it will consume exactly the same amount of fuel at idle whether it is in gear or out of gear. Most newer cars are computer controlled, and the engine is going to idle at a speed determined by the computer. If you put a load on the engine (like having it in gear with an automatic transmission) then the computer will compensate for the load and allow more fuel to go into the engine to bring it back up to the desired idle speed.
Of course, the amount of fuel required to bring the idle up is tiny. We’re talking about savings that would amount to pocket change over the course of a year.
At idle, all of the wear and tear on the transmission is on the parts that are used to moving the entire weight of the car around, so the wear and tear of sitting at idle is pretty negligible. Shifting in and out of gear puts wear and tear on other parts of the transmission and you might end up causing yourself transmission problems if you do it too much. Over the life of the car you might save 10 or 20 bucks in gas and cost yourself an $800 transmission job.
For a stick shift transmission, you aren’t going to save any gas at all by shifting into neutral but you will save wear and tear on your throwout bearing.
What you do save wear and tear on if you put manual transmission in neutral and take you foot off the clutch pedal is wear and tear on the clutch release bearing and the thrust bearings on the crankshaft. I always put my manual transmission in neutral and let up on the clutch at stop signs. Of course, shifting does wear the shuft fork assembly to some extent and that’s a minus.
With my automatics I never do although it would save a little money. However, shifting the transmission into neutral does create some wear on the gearset which might negate the fuel savings. If you trade cars frequently the wear won’t make any difference to you.
Sadly, like so many things, it’s a tradeoff and we don’t have a lot of data on which to base a decision.
Not really straining against the brakes, but rather your torque converter, which is the whole point of automatic transmissions. The hydraulic fluid tries to spin your transaxle, but it’s locked by virtue of your locked brakes. If you switch to neutral, then the turbine and stator are spinning freely… I wonder if this would actually consume more fuel?
Technical question for a car person.
I just ran a test in my parking lot with my 2002 Saturn Ion 4 door and my wifes 2006 Saturn Ion quad coupe.
In neutral the tachometer was just a fraction under the 1K marker.
Switching into drive dropped the needle noticeably. This held true in both cars but was more noticeable in the 2001 Ion over the 2006 Ion.
Does this indicate Im using less gas in drive than neutral or do I just not understand the mechanics involved here?
No there is a saving by switching to neutral. But it isn’t much. Volvo tried a transmission that automatically shifted to neutral when at a stoplight. However they could never get the software quite right and discontinued after a short run. I do not recall of hearing of any decreased fuel mileage complaints after the transmission software was changed.
In a standard, idling with the clutch down wears the throwout bearing, and (in most cars) the thrust bearings on the engine crankshaft. In neutral, the engine is churning the oil in the transmission, so is using MORE fuel. This is very noticeable on motorcycles…when the transmission is cold, they will frequently idle OK with the clutch in, but will stall in neutral.
Automatic transmissions churn more oil with the torque converter stalled than they do in neutral. Churning the ATF converts the mechanical work of the engine into heat. Putting them in neutral while stopped saves a little fuel, and helps keep the transmission from overheating. Probably not an issue in “normal” driving, but might matter if you are stuck in heavy traffic on a 100 degree day.
Many automatic transmissions have a minimal detent between neutral and drive to facilitate taking them out of gear at traffic lights and such. You might have to push a button with your thumb, for example, to move from D to L, but not need to press the thumb button to move between neutral and drive.
In my experience, even fuel injected cars have a lower idle speed in gear than in neutral. You’re probably correct that the computer opens the idle air controller a little to keep it from stalling too much. Even so, the air passing through the engine (and thus the fuel consumed) is roughly proportional to the intake manifold pressure times the engine speed. You’d be raising the pressure but lowering the engine speed. I don’t see how you could know which has more effect without doing analysis.
Yes indeed. However, I do believe the engine is doing more work pumping oil around with the automatic transmission in gear than if it’s in neutral. This would result in increased fuel consumption in gear.
Probably not, most systems now have a constant idle speed. In gear out of gear, a modern car will idle at the same speed. Typically it is in a 25-50 rpm range is considered normal. For example a friend’s car I messed with Thursday had an idle speed of 725-775. In gear or out, this is the idle speed.
As I said before, with an auto trans, you are doing less work in neutral, but I doubt you would be able to see the difference in your fuel mileage.
Kevbo in a car’s manual transmission all that turns when you are in neutral with your foot off the clutch is the first motion shaft, and the layshaft. Not much energy to move those, you can easily spin them by hand (assuming you have the trans out where you can reach the shaft).
If the countershaft is turning all of the gears are turning except for reverse idler. The thing is, in neutral none of the dog teeth are engaged so as to lock the output gear to the propellor shaft.
If the layshaft is turning, then all the forward gears on the mainshaft, which are driven by gears pressed on or cut integral to the layshaft, are also turning. Only reverse isn’t turning. No?
:smack:
You are correct, but it still takes very little energy to turn them. It is very easy to spin a first motion shaft, lay gear and the other forward gears when the box is in neutral.
No doubt. It takes little effort to stir oil and turn meshed gears when the gears aren’t loaded.
Just making sure that the dope dispensed is the straight dope. 
