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Author Topic: With an auto, should you shift to neutral at lights to save fuel? Back to Topics
FreddFfish

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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?
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dontuknowOH
Champion Author Ohio

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Message Posted: Feb 8, 2015 9:06:47 AM

I've never had any experience at washing hogs, only two wheeled ones. Those torque converters always spin when the engine is running, always spin when the vehicle is in motion also. they always spin in sync with the engines running RPMs as that varies in its useable speed range.

The T/Q slightly loads the vehicle's engine with a pumping effect slight resistance while at idle when the transmission is coupled in drive, and ready to respond at moving the vehicle into motion. It also acts as a fluid transfer clutch when in gear/drive.

Holding the brake pedal stops the initial idle energy which is an engine energy load of convenience(no positive locking manual clutch) for the driver to engage for movement/car motion.

Neutral relaxes the idle restive energy engine load of the T/Q action. If the brake lights go off a small amount of electrical energy is saved relaxing the vehicle's alternator duty somewhat. Alternators have a varied duty to keep the entire electrical system charged/balanced at the central battery energy source. Ever had a Dead/Drained Battery?....(Hood open)....

When an engine is fully warmed the RPM indicator will only show a slight temporary change(movement) because the ECM is readjusting the engine idle correction to whatever the driver is manually monkeying with, Sorry! The Driver can do that, like changing the cruise, heater/ac mirrors, most other functions of choice also.

BUTT! Your ECM Brain is making necessary other adjustments to your modern operating system as OEM designed, You are an on-looker. Maybe learning, most of the time. You will have to talk to your New phone about it...G-L!
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luvmyrv
Champion Author Winnipeg

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Message Posted: Feb 7, 2015 9:05:46 PM

How is that going to save any fuel? Hogwash!
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Sugarshaneo7
Veteran Author Michigan

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Message Posted: Feb 7, 2015 11:33:56 AM

I do that so some idiot doesn't hit me from behind and causes damage to my engine.

I'm smarter than most I suppose.

[Edited by: Sugarshaneo7 at 2/7/2015 11:34:36 AM EST]
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JohnCur
All-Star Author New Jersey

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Message Posted: Feb 7, 2015 10:34:09 AM

If you shift to N rpm go up...check tach
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dontuknowOH
Champion Author Ohio

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Message Posted: Feb 7, 2015 9:29:34 AM

All My vehicles are one click away from drive--neutral mode, everything else is safety locked out on the shifter. N../D.. mode is a shove forward/backward. like click/click.

Any other selections must be to avoid the lock mechanism, mine works better than the turn signal lever doing left or right, detents or not used. I Love my daily driver, it has only 3 minor faults that I would improve on, maybe change.
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weddy11
Champion Author Phoenix

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Message Posted: Feb 7, 2015 9:07:31 AM

No, If I were to move the lever, it would be to park.
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PaylessKY
Champion Author Kentucky

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Message Posted: Feb 7, 2015 8:45:46 AM

Not with todays transmissions.
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twt
Champion Author Virginia Beach

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Message Posted: Feb 5, 2015 6:37:25 AM

Sounds like somebody is paranoid, about gas consumption.
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mybigtruck
Champion Author San Jose

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Message Posted: Feb 5, 2015 1:33:25 AM

I see about a 40% drop in fuel consumption while idling in neutral vs drive in my diesel.
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redfish67
Champion Author Dallas

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Message Posted: Feb 4, 2015 1:48:00 PM

no
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speedfreek
Rookie Author Edmonton

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Message Posted: Feb 4, 2015 11:37:24 AM

If you have an obd port on your car, get one of those elm327 Bluetooth odb transmitters and get an Android device and grab Torque Lite. That'll tell you if you're saving fuel or not. Just watch home much fuel it's sending/requesting and watch the upstream o2 sensors, etc...

My guess is if you're still cold, get a hotter thermostat and get a weather front. The longer you're in open loop on a cold start the more fuel you waste. Maybe plug your car for 1/2 an hour before you leave on your trip...

[Edited by: speedfreek at 2/4/2015 11:38:17 AM EST]
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dontuknowOH
Champion Author Ohio

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Message Posted: Feb 4, 2015 9:52:58 AM

I have found that sometimes if a vehicle has a marginal old aged battery (last stages of use) then when colder Seasons arrive the engine behaves a bit poorly at any time. The results can be that the cold voltage drop at a cold start can often cause the ECM to loose it's sensor derived settings.

Cold cranking speed, injector pulse rate, closed loop settings, fast idle speed, ign. advance timing, tranny shifting, ETC. = many disruptions, but still performing better for a given day or weather reversal(warmer)may then improve engine run things again temporally.

Saying sometimes battery voltage excessive drop off on a colder engine start up may be the culprit, The cold cranking amp load possibly becomes below the minimum for successful ECM/Sensor proper control/adjustments. Doesn't hurt to check that first.

Saving fuel in neutral after vehicle has warmed to normal for Me would require a longer time interval of driving, like a check monthly after several hours of engines run time/traffic events. That ratio varies......
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JohnCur
All-Star Author New Jersey

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Message Posted: Feb 4, 2015 8:33:41 AM

no
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Heavyblaze
All-Star Author Pennsylvania

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Message Posted: Feb 4, 2015 6:26:04 AM

no
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hoopitup2000
Champion Author Virginia

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Message Posted: Feb 4, 2015 6:15:36 AM

I do sometimes, especially if the choke is still on fast idle.
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RalphHightower
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Message Posted: Feb 4, 2015 6:09:46 AM

no
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dieseldemon
Veteran Author Houston

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Message Posted: Feb 3, 2015 5:50:23 PM

No I don't think so
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dontuknowOH
Champion Author Ohio

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Message Posted: Feb 3, 2015 5:47:54 PM

If your vehicle stays idling at a high rate much longer than normal say on an older model vehicle, the thermostat could be getting sluggish, and colder weather will make it's action even worse.

I once changed to a lower temp thermostat for Summer driving in a warmer climate out of state. When back to our home during Fall season, Mo "80's" model vehicle took much longer to idle back, each startup. The 180* installed was the problem, being out of order with it's ECM program, and I forgot to change it back to the 192* stat.(called for). Ohio need the proper stat or one not aged/sluggish. They do have a lifespan........
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ray44512
All-Star Author Ohio

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Message Posted: Feb 3, 2015 5:27:30 PM

My car idles high when cold, so I do slip it into neutral at red lights. Its not for fuel economy but rather keeping the car from pulling.
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Robert8716
Rookie Author Portland

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Message Posted: Feb 3, 2015 11:44:45 AM

no
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carinthuist
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Message Posted: Jan 29, 2015 11:14:01 AM

no
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RalphHightower
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Message Posted: Jan 29, 2015 6:14:23 AM

no
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dontuknowOH
Champion Author Ohio

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Message Posted: Jan 28, 2015 10:08:09 PM

I do at certain lights, this avoids braking and often maintaining close to traffic speeds. It always takes several seconds for waiting cars ahead to clear/move out on the green, and I often take advantage of that condition.

There is a small savings if waiting stopped at idle in N... mode. My ECM adjust the engines idle speed requirements for the other operations loads. If the driver watches their RPM/engine tach. they may see the slight correction/variation movement reading. Often not much because of the accessories and other electrical demands that the alternator is handling automatically.

Larger engines show less change due to their greater idle torque than a smaller 4 cylinder engine. More cylinders = more brut = more idle fuel cost. Your left foot might get bored/restless with an automatic using N....
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twt
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Message Posted: Jan 27, 2015 6:37:35 AM

A waste of time.
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hoopitup2000
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Message Posted: Jan 27, 2015 6:26:23 AM

I usually do.
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dontuknowOH
Champion Author Ohio

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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.....
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jrferrari
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Message Posted: Jan 10, 2013 11:05:59 AM

Turning the engine off would probably save more.
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dontuknowOH
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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
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Jeff1226
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Message Posted: Jan 8, 2013 2:25:48 PM

I don't
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HotRod10
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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).

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JasTheAce
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Message Posted: Dec 28, 2012 5:13:17 PM

no
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hi5hi5
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Message Posted: Dec 17, 2012 9:41:46 PM

no
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jonjon57
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Message Posted: Dec 17, 2012 7:42:13 PM

No
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Snowchoux
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Message Posted: Dec 16, 2012 11:36:33 AM

No, or may be yes
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RalphHightower
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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.
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dontuknowOH
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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....
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dgsteven
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Message Posted: Dec 16, 2012 3:21:41 AM

no, always in D
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Casey225
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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.
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PaylessKY
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Message Posted: Dec 16, 2012 12:13:57 AM

Not with todays transmissions.
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jonjon57
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Message Posted: Dec 15, 2012 9:27:11 PM

No
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the1roadhog
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Message Posted: Dec 15, 2012 7:42:35 AM

Too hardcore for me
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dontuknowOH
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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

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Dennis783
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Message Posted: Dec 12, 2012 7:41:26 AM

just remember to put it back in gear before you stomp on the gas
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DanFMA
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Message Posted: Dec 12, 2012 5:58:30 AM

No.
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skidsteer85xt
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Message Posted: Dec 7, 2012 9:47:22 PM

no
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jack4141
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Message Posted: Dec 7, 2012 4:15:09 PM

Nope
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BlueberryFocus
All-Star Author Rochester

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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.
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allnighter
Rookie Author Atlanta

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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.
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bosoxlin
Rookie Author Boston

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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
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rumbleseat
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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.
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dontuknowOH
Champion Author Ohio

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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.
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