Not Logged In Log In   Sign Up   Points Leaders
Follow Us    7:04 AM

Message Forum - Read Message

Category: Fuel Economy > Topics Add to favorite topics   Post new topicPost New Topic
Author Topic: With an auto, should you shift to neutral at lights to save fuel? Back to Topics
FreddFfish

Veteran Author
Orange County

Posts:302
Points:354,505
Joined:Aug 2012
Message Posted: Oct 25, 2012 12:57:25 AM

Would there be any point in shifting to neutral when stationary to save fuel with an auto?

Most drivers seem to sit at the light in drive, with their foot on the brake. Wouldn't the Torque Convertor use more energy while spinning away, compared to slipping it into neutral?
REPLIES (newest first) Post a Reply
Profile Pic
dontuknowOH
Champion Author Ohio

Posts:3,537
Points:61,125
Joined:Aug 2009
Message Posted: Jan 10, 2013 9:40:19 PM

Turning off the engine with a vehicle in motion can cause serious damage to an automatic tranny,the pump lubrication stops circulating,stops the cooling of internal rotating parts that are driven by the drivetrain as the vehicle moves.Intence heat develops at the tranny.

Also power steering assist is lost,vacumm stops,power brakes loses p... brake abilities,abs brakes can be affected,if engine is stopped while going back to drive mode more problems can be the result,by upsetting the ECM with erattic signals,converter lock-up feature risks possible.

Shutting off the engine,for long waits while vehicle is stopped won't cause any harm and saves fuel,but if placed in park,then when starting,the back-up lamps gets flashed,sometimes the driver behind gets the jitters and blows their horn at guess who! Not always.....

If your coolant fans run with engine off while waiting,the battery pulls down a little and the altenator then charges heavy after restart to still drive the fans and build back the battery energy using a bit more fuel reaching normal again,depends on type of weather.....
Profile Pic
jrferrari
All-Star Author Orlando

Posts:652
Points:172,990
Joined:Jan 2011
Message Posted: Jan 10, 2013 11:05:59 AM

Turning the engine off would probably save more.
Profile Pic
dontuknowOH
Champion Author Ohio

Posts:3,537
Points:61,125
Joined:Aug 2009
Message Posted: Jan 10, 2013 8:58:38 AM

When you start the vehicle from a cold start,all accessories,lights off, notice how much the engine rpm drop when changing to drive. Put the park brake on first firmly,this will keep the brake lamps off also but some vehicles won't go into drive unless the brake pedel is applied safety first,b..lights on.

The drop in rpms is a result of the T..converter coupling with the tranny releasing fluid clutch action but causing an engine load,later with lights,heater blower,and other accessories on adds extra loads to the engine by the altenator demands to handle the vehicle battery's condition and all electrical demands.

Remember the higher E..rpms mean more fuel,richer balance because of the cold start-up,later that extra fuel is reduced as warm-up goes to normal E..temps,still the converter/tranny load continues at idle,when stopped, along with the altenator keeping up to your choices/automatic demands (OEM system) (safety,cooling,etc.)

Remember also that idle loads vary by the automatic function system controls,but are regulated by the ECM to keep idle speed from changing > dropping,which would probably stall the engine. Your choices have a lot to do with varing the load rate of the altenator at any speed,so whatever extra fuel energy is needed gets used automatically,RPMs simply show rpms,hints maybe for a split second at idle (crude at low readings on the dial). Crude like wiper blades/ice scrapers LOL
Profile Pic
Jeff1226
Sophomore Author Flint

Posts:127
Points:8,100
Joined:Feb 2012
Message Posted: Jan 8, 2013 2:25:48 PM

I don't
Profile Pic
HotRod10
Champion Author Wyoming

Posts:3,592
Points:60,755
Joined:Oct 2006
Message Posted: Jan 8, 2013 11:27:07 AM

Doubtful that it would save much of anything in fuel cost, but it might cost you a very expensive transmission, automatic trannys are not made to be manually shifted all the time.

Transmission damage is especially likely if you happen to bump it a notch too far and end up in reverse. My dad did that once and the engine and transmission had to replaced, granted he was going 45mph at the time (Ford Van POS).

Profile Pic
JasTheAce
Champion Author Raleigh

Posts:3,507
Points:772,235
Joined:Nov 2012
Message Posted: Dec 28, 2012 5:13:17 PM

no
Profile Pic
hi5hi5
Rookie Author Honolulu

Posts:55
Points:10,795
Joined:Dec 2012
Message Posted: Dec 17, 2012 9:41:46 PM

no
Profile Pic
jonjon57
Champion Author Raleigh

Posts:2,597
Points:727,515
Joined:May 2011
Message Posted: Dec 17, 2012 7:42:13 PM

No
Profile Pic
Snowchoux
Champion Author Missouri

Posts:1,003
Points:145,635
Joined:Sep 2012
Message Posted: Dec 16, 2012 11:36:33 AM

No, or may be yes
Profile Pic
RalphHightower
Champion Author South Carolina

Posts:5,982
Points:1,292,045
Joined:May 2011
Message Posted: Dec 16, 2012 9:52:43 AM

No. But if I have to stop at a RR crossing for a long train, I'll turn off the engine.
Profile Pic
dontuknowOH
Champion Author Ohio

Posts:3,537
Points:61,125
Joined:Aug 2009
Message Posted: Dec 16, 2012 9:14:20 AM

I don't always slip in neutral at each short traffic red light/wait, often I try to catch the greens and keep moving. Summer with AC on I try even to decell ahead of time on notice that I must stop or nearly stop for a red + traffic line-up ahead.

If the vehicle stays in motion those cooling boost fans stay off even with AC on,brake lamps stay off,the engine's burn energy/heat cycle rests a bit,fuel to keep all operations ready for resuming is often reduced.Tranny/converter temps drop off a little if in neutral.

The sooner you release the go pedel on seeing the decell coming up ahead the better choices to make ,it's your gas flowing if the pedel stays down,often it takes a bunch of seconds for those vehicles ahead to get moving. Yes each time you resume to a higher cruise speed Extra fuel energy gets used up to due so.If you cause the tranny to down-shift ,again that action requires even More Fuel usage. Be Happy it was your choice and that's your gas in the tank I hope....
Profile Pic
dgsteven
Champion Author Los Angeles

Posts:3,400
Points:809,825
Joined:Oct 2012
Message Posted: Dec 16, 2012 3:21:41 AM

no, always in D
Profile Pic
Casey225
Rookie Author Baton Rouge

Posts:91
Points:94,215
Joined:Nov 2012
Message Posted: Dec 16, 2012 1:56:30 AM

This will not make much of a difference with engine load, however while in traffic shifting to neutral may help prevent over heating.
Profile Pic
PaylessKY
Champion Author Kentucky

Posts:11,330
Points:2,182,325
Joined:Oct 2008
Message Posted: Dec 16, 2012 12:13:57 AM

Not with todays transmissions.
Profile Pic
jonjon57
Champion Author Raleigh

Posts:2,597
Points:727,515
Joined:May 2011
Message Posted: Dec 15, 2012 9:27:11 PM

No
Profile Pic
the1roadhog
Champion Author Atlanta

Posts:11,530
Points:2,624,735
Joined:Jun 2007
Message Posted: Dec 15, 2012 7:42:35 AM

Too hardcore for me
Profile Pic
dontuknowOH
Champion Author Ohio

Posts:3,537
Points:61,125
Joined:Aug 2009
Message Posted: Dec 15, 2012 1:42:03 AM

I believe the amount of fuel savings will vary,depends on what size engine is in use,V/6 and V/8s have more idle torque than an in-line 4 cyl,also todays altenators are designed to produced way more amps/wattage than older vehicles.

Also the amount of safety devices/accessories turned on due to different driving conditiond,along with the amount of brake lights lite,then again the auto tranny/converter loading when in drive causes the ECM to signal the idle circuits > EFI/air balance control to hold correct idle speed as programed.

If those energy users, say on a rainy cold night are all turned on sitting at a long T..light,whatever,then a 4 cyl engine with less torque VS the V design larger Ltr. engines then needs a boost of idle fuel/air to sustain correct idle speed > results in more fuel.

The larger engines being of V block design instead of in-line just have the extra torque (grunt ability over the smaller size 4 cyl,non V block)types. Vee design engines just have more low/mid rpm torque,ask a Harley D... motorcycle rider. Or look at the amount of other V engine bikes,Awsom!

Just saying the amount of idle savings can vary for each drivers vehicle is differient by habits,engine type/size,weather/climate conditions, HMmmm.... Like pulling a parade Float.... LOL

Profile Pic
Dennis783
Champion Author Des Moines

Posts:16,175
Points:3,280,995
Joined:Sep 2005
Message Posted: Dec 12, 2012 7:41:26 AM

just remember to put it back in gear before you stomp on the gas
Profile Pic
DanFMA
Champion Author Massachusetts

Posts:3,710
Points:1,673,915
Joined:Apr 2008
Message Posted: Dec 12, 2012 5:58:30 AM

No.
Profile Pic
skidsteer85xt
Champion Author Indiana

Posts:10,814
Points:787,850
Joined:Oct 2012
Message Posted: Dec 7, 2012 9:47:22 PM

no
Profile Pic
jack4141
Champion Author Alabama

Posts:3,950
Points:889,630
Joined:Mar 2011
Message Posted: Dec 7, 2012 4:15:09 PM

Nope
Profile Pic
BlueberryFocus
All-Star Author Rochester

Posts:559
Points:173,980
Joined:Feb 2012
Message Posted: Dec 6, 2012 11:31:23 PM

This could be a good expirament actually... anyone with a scan tool willing to check out engine load while idling in gear vs in park or neutral? The higher the engine load, the higher the fuel consumption.
Profile Pic
allnighter
Rookie Author Atlanta

Posts:35
Points:661,840
Joined:Sep 2012
Message Posted: Dec 6, 2012 3:07:47 PM

It would only slightly (less than 100 RPM) alter your idle. It wouldn't save you hardly any gas at all. Maybe 8 oz or so over a couple tanks.
Profile Pic
bosoxlin
Rookie Author Boston

Posts:1
Points:220
Joined:Dec 2012
Message Posted: Dec 6, 2012 1:57:30 PM

neutral makes sense to me in a standard trans but would neutral make sense in an automatic?

I am very ignorant about cars and just want to learn! Please bear with me as my questions may seem elementary if not stupid. This is how I learn! I thank you in advance
Profile Pic
rumbleseat
Champion Author Winnipeg

Posts:25,292
Points:3,830,710
Joined:Oct 2002
Message Posted: Dec 6, 2012 12:06:52 PM

Not sure why coasting down-hill in neutral is part of the shift to neutral at lights, but that bears comment.
Most modern cars will use less gas when coasting down hill in gear than they will by switching to neutral. In gear, the transmission keeps the engine turning and so no or very little gas is required.
If you have an AWD, you risk damage to some vehicles. Read a Subaru manual.
Profile Pic
dontuknowOH
Champion Author Ohio

Posts:3,537
Points:61,125
Joined:Aug 2009
Message Posted: Dec 6, 2012 11:37:03 AM

Yes I sort of have a feeling for my altenator,being it works very hard keeping up with todays energy loads > Driving safety head-lamps ,electric power steering,abs brake systems,powerful music systems Heater/AC,heated seats,mirrors/rear defrosters,wipers,coolant fans,well the list goes on > electric auto trannys,power antennas,accessory recepts,etc,many brake lights,well I think the newest cars have less loss at the automatic tranny converter idle loading. Still the alties take a beating of heat/highRPMs.
Profile Pic
WEDDY
Champion Author Phoenix

Posts:5,964
Points:1,635,270
Joined:Oct 2009
Message Posted: Dec 6, 2012 8:56:19 AM

I don't.
Profile Pic
gougedQC
Champion Author Montreal

Posts:5,656
Points:76,885
Joined:Apr 2008
Message Posted: Dec 1, 2012 6:40:51 AM

I shift to neutral --in the city--on long downhills, and from several hundred metres toward stoplights.. it does save gas, and also wear on the brakes

been doing it for many years, never a tranny problem

[Edited by: gougedQC at 12/1/2012 6:42:09 AM EST]
Profile Pic
dontuknowOH
Champion Author Ohio

Posts:3,537
Points:61,125
Joined:Aug 2009
Message Posted: Nov 30, 2012 10:42:50 PM

rumbleseat; The Whoopee! for the total savings of aprox. .001% seems a bit too fixed considering there probably are over 50+ different engine sizes in use with automatic transmissions across the country,also with no data on age,design,condition,HP ratings,reg/premium fuel requirments...etc.

The .0001% is surely a narrow range of total saving estimate maybe.... LOL
I guess the > could possibly < extend that range t another % figure....
Profile Pic
rumbleseat
Champion Author Winnipeg

Posts:25,292
Points:3,830,710
Joined:Oct 2002
Message Posted: Nov 30, 2012 7:17:30 PM

In an auto transmission car, the savings could possibly total approximately .001% of your gasoline consumption.
Whoopee! Not worth the bother.
Profile Pic
dontuknowOH
Champion Author Ohio

Posts:3,537
Points:61,125
Joined:Aug 2009
Message Posted: Nov 30, 2012 9:22:06 AM

MertieMan; I reviewed a few posts,then chuckled when I was reminded by yours? I have experienced auto trannies, older ones having tranny fluid sucked into the engine due to a bad diaphram in the modulaator control valve (engine burning the tranny fluid away).

The chuckle came when I saw that > the tranny doesn't burn that much gas because of design,when waiting,behing held back from motion when in drive. I'm hoping another cup of coffee,Sunday morning coffee, would help me to understand that a tranny can suck gas from the engine,being opposite from my encounters of the lost tranny fluid.

I can agree about some drivers reving up at lights for attention mostly the vehicles often have good sounding pipes(needing attention)maybe... it's a new texting cover-up technique.... Coffee time !..... LOL
Profile Pic
dontuknowOH
Champion Author Ohio

Posts:3,537
Points:61,125
Joined:Aug 2009
Message Posted: Nov 30, 2012 2:23:09 AM

I see a differience between while sitting at a red light waiting,compared to when approaching a red light still in motion,relating to fuel savings by slipping into neutral.

Any vehicle I have driven,when one slips into neutral aproaching a seen red light First must get off the go pedel, again First, before shifting out. So the Sooner the pedel is released fuel usage is reduced also sooner.

The light is going to due whatever but the driver's reaction is where the savings occurs or not,granted it's minor but each time savings add up to better mileage.
Profile Pic
Houckster
Champion Author Atlanta

Posts:11,107
Points:768,535
Joined:Sep 2003
Message Posted: Nov 29, 2012 11:32:08 PM

There is no advantage to putting an automatic transmission in neutral during period of idling. I've never seen any evidence to the contrary.
Profile Pic
hrspwr77
Champion Author Georgia

Posts:1,478
Points:120,585
Joined:Oct 2012
Message Posted: Nov 29, 2012 12:55:22 PM

I don't do this to save gas. In certain situations I will do it for mechanical reasons, especially on a hot summer day
Profile Pic
jonjon57
Champion Author Raleigh

Posts:2,597
Points:727,515
Joined:May 2011
Message Posted: Nov 29, 2012 7:20:31 AM

Nope
Profile Pic
RalphHightower
Champion Author South Carolina

Posts:5,982
Points:1,292,045
Joined:May 2011
Message Posted: Nov 29, 2012 6:19:09 AM

I don't.
Profile Pic
BlueberryFocus
All-Star Author Rochester

Posts:559
Points:173,980
Joined:Feb 2012
Message Posted: Nov 29, 2012 12:20:23 AM

Like other's have said, it's up to the driver as to whether its worth the hassle or not. The savings aren't very significant per stop, but given that over a lifetime the average person spends about 6 months waiting at stoplights, it adds up. Does that mean people do it? No. It would actually be better if more cars would shut the engine down after being stopped for a certain period of time.
Profile Pic
DeserTBoB
Champion Author California

Posts:1,757
Points:292,945
Joined:Aug 2012
Message Posted: Nov 28, 2012 11:47:20 AM

On a manual transmission, save yourself repairs...slip into neutral at ALL stops. Sitting there with you foot mashing the throw-out bearing is just plain stupid, but most drivers are stupid anyway, so it figures that most do it.
Profile Pic
DeserTBoB
Champion Author California

Posts:1,757
Points:292,945
Joined:Aug 2012
Message Posted: Nov 28, 2012 11:45:40 AM

Shifting into neutral at a stop for a signal is only advisable under a couple of extranormal conditions. One would be if the engine is running hotter than normal in stop-and-go traffic. The heat load generated by the torque converter at at stall is not that much, but if you're running hot, the last thing you want to do is add more heat load to the cooling system. It also helps to elevate the engine speed when "cooling out" an engine, as it speeds coolant flow. You see idiots all the time in line at junk food joints with their cars in drive...this is BAD for the transmission, as the heat load builds up due to low engine speed and cooks the fluid. Always shift into neutral and set your parking brake (or shift to park) in that situation. Better yet, just shut the engine OFF if you're going to be there for more than a couple of minutes, similar to what you'd do at an RRX for a long freight. No, you don't necessarily "use more energy" at a red light by having it in drive rather than in neutral. The savings are inconsequential when it comes to fuel economy.
Profile Pic
dontuknowOH
Champion Author Ohio

Posts:3,537
Points:61,125
Joined:Aug 2009
Message Posted: Nov 28, 2012 11:02:23 AM

Just saying your RPM OEM Indicator reads about the same both ways tells me you have EFI controlled by its Boss > The ECM Brain.
So idle speed is controlled automaticly,any choices the driver makes may cause ithe speed to vary fora short second or two but correction takes place if(everything operates as normal) The RPM reading is only that,not a fuel usage guage, it does relate to engine crank/converter speed. Engine loading will show a drop or rise at times but not a measure of actual amounts. HAGDay !
Profile Pic
2amy
Champion Author Fresno

Posts:1,857
Points:708,815
Joined:Feb 2011
Message Posted: Nov 27, 2012 6:03:34 PM

With an automatic transmission I cant see the point. The rpm's are about equal from sitting in drive or neutral.
Profile Pic
dontuknowOH
Champion Author Ohio

Posts:3,537
Points:61,125
Joined:Aug 2009
Message Posted: Nov 27, 2012 5:16:16 PM

I've slipped into neutral many times when approaching a stop,never clutching but simply easing off the go pedel enough,feeling the drive train load ease off balance with the engines energy, then drop out of gear with a std. tranny to neutral.

Yes the clutch comes back into play when resuming or starting motion again,saving fuel while at idle waiting,brakes off,lessing wear/tear on clutch T-O..bearing and pressure plate,legs and feet.

Idle fuel stays normally at a minium,takes a second to drop into gear and go,if slick conditions persist I have often started off in 2nd gear to elliminate wheel spin. W-F-Me
Profile Pic
RRBC
Champion Author Victoria

Posts:5,143
Points:1,085,820
Joined:Oct 2011
Message Posted: Nov 26, 2012 9:31:31 PM

I don't, but interesting to read.
Profile Pic
Brunduski
All-Star Author Missouri

Posts:611
Points:282,690
Joined:Jun 2012
Message Posted: Nov 26, 2012 7:18:02 PM

For automatics, this is an issue but to be honest, the fuel savings would be minuet at best. As others have said, unless you are driving in solid traffic all the time with a lot of lights, it would increase. However, when you actually put it into perspective as far as dollars and cents, it might only save you $20 a year. Not really worth the hassle IMHO.
Profile Pic
Endoman5000
All-Star Author Michigan

Posts:854
Points:825,350
Joined:Jan 2012
Message Posted: Nov 26, 2012 6:32:15 PM

I shift into neutral when getting off the highway and I have to stop at the end of the ramp. Not sure if I am doing damage to the car but it does help the mpg's
Profile Pic
1007
Champion Author Michigan

Posts:2,291
Points:1,533,150
Joined:Jan 2008
Message Posted: Nov 26, 2012 6:23:55 PM

No I do not shift into N I believe this is really a push over other driving changes.
Profile Pic
rual817
Sophomore Author Dallas

Posts:118
Points:245,780
Joined:Nov 2011
Message Posted: Nov 26, 2012 2:57:50 PM

Hypermiling CAN save your FE. Don't just put in "N" at the light, and Don't "gas" it all the way to the light. Let off the pedal way early and put it in "N" and coast to the light. While at the light "N" seems to be less Torque on the motor. Less torque means the engine is spinning more freely... using less fuel. IMHO
Profile Pic
Banjoe
Champion Author Winnipeg

Posts:8,398
Points:1,214,355
Joined:Apr 2011
Message Posted: Nov 26, 2012 8:41:22 AM

This topic started me experimenting with this concept and, because the TDI has a mileage/fuel useage output, it's simple to test various options.

Shifting the automatic into neutral reduces gas (diesel) consumption a bit. More of a savings comes from shutting off the heater fan and even a little bit comes from the radio.

I had assumed that holding the beast back with the brake while in gear would provide the lowest consumption just didn't prove to be true. Free spinning in neutral is the fuel saving way.

Profile Pic
the1roadhog
Champion Author Atlanta

Posts:11,530
Points:2,624,735
Joined:Jun 2007
Message Posted: Nov 26, 2012 7:47:30 AM

nitzy
Profile Pic
dontuknowOH
Champion Author Ohio

Posts:3,537
Points:61,125
Joined:Aug 2009
Message Posted: Nov 25, 2012 2:28:06 PM

I often get annoyed when I open my gastank filler cap,I also understand other points of ones view,I really get annoyed when a station charges for air pressure but then again expect the motorist to come in and buy items at higher prices,then wait in line,to leave for only gas sales. I agree pennies aren't worth much but if you pump over an even dollar amount,the attendant wants you to chuck it out while smiling.

"A penny saved is a penny earned" On this planet maybe? Who said that?
Post a reply Back to Topics