View Full Version : Coasting w/ auto trans


dz302
01-24-2008, 02:39 PM
Is it OK to coast while driving (to extend fuel economy) and then place back into drive while still moving? Coasting really helps mileage "but" I don't want to hurt my transmission.

Thanks.

Dondirtyj
01-24-2008, 02:42 PM
why don't you just keep your revs low??? or if your havent cleaned your fuel injectors lately try buying a bottle of cleaner and putting it in your tank

HeathenBrewing
01-24-2008, 02:51 PM
Coasting in your box will NOT help mileage. Engines are a lot different in 2006 then they were in 1976 Read some more about VVTI and it will explain why coasting in N will not help you save gas.

Nastos
01-24-2008, 02:57 PM
i know ive noticed in the m/t it saves gas to coast instead of down shifting its just harder on your brake pads

if you wanted to coast around town you shoulda just opted for a manual they are generally a lil better on gas anyway

HeathenBrewing
01-24-2008, 03:02 PM
i know ive noticed in the m/t it saves gas to coast.....

I too have the MT, but noticed no MPG increase shifting into N while declining. The VVTI is smarter than that. This is not an old carbureted car.

.....instead of down shifting its just harder on your brake pads

Still dont understand the whole downshifting thing....Im not racing my xB. Besides, new brake pads are cheaper than new MT parts.

Auto users beware: Linkages!

Shifting back and forth out of neutral on most automatics, while at speed, is excess wear on the linkages that serves no purpose other than generating revenue for mechanics. You also run the risk of putting the transmission in reverse on about any automatic manufactured since the mid 60s, which if youre in top gear in a first generation auto featuring a locking torque converter, will be exciting at best and generate a great deal of money for a mechanic someplace (and his parts suppliers,) if you don't manage to total the car in the process.

Nastos
01-24-2008, 03:09 PM
ive done multiple tests and it does improve by .5 - 1mpg not much but it only makes sence the engine is revving during downshifting higher than if you just put it in n vvti is smart but physics are smarter

HeathenBrewing
01-24-2008, 03:19 PM
ive done multiple tests and it does improve by .5 - 1mpg not much but it only makes sence the engine is revving during downshifting higher than if you just put it in n vvti is smart but physics are smarter

It is entirely possible the savings you are getting from doing this is coming from your desire to get better mileage. The VVTI turns the fuel delivery "off" when you lift your foot from the accelerator. It feeds more fuel to the fuel injectors with the trans in N than it does with your trans in gear and your foot off the gas.

Nastos
01-24-2008, 03:20 PM
lol you cant put it in reverse while going more than 10mph it just grinds so bad you automatically know you effed up... down shifting is a great way to slow down faster.. im not even going to argue it if you know what your doing downshifting it will not harm your mt... i guess its just me ive always had mts and never once had a tranny or clutch prob and have always downshifted and any one who is true to the clutch will call you a noob if your just throwing it in n and slamming the brakes from 4th gear.. even autos downshift themselves its a good way to slow down your engine and your whole car and when done right will not cause any damage to your clutch flywheel or any other tranny component

Nastos
01-24-2008, 03:23 PM
ive done multiple tests and it does improve by .5 - 1mpg not much but it only makes sence the engine is revving during downshifting higher than if you just put it in n vvti is smart but physics are smarter

It is entirely possible the savings you are getting from doing this is coming from your desire to get better mileage. The VVTI turns the fuel delivery "off" when you lift your foot from the accelerator. It feeds more fuel to the fuel injectors with the trans in N than it does with your trans in gear and your foot off the gas.

one last thing why would your foot be on the accelelerator while in neutral? im sure it is bad for an auto to be shifting in and out of n and d... but its perfectly safe for a m/t

HeathenBrewing
01-24-2008, 03:25 PM
lol you cant put it in reverse while going more than 10mph it just grinds so bad you automatically know you effed up...

Ok....sounds right. I have not owned a AT car before...at least not an auto made adter 1970.

...down shifting is a great way to slow down faster.. im not even going to argue it if you know what your doing downshifting it will not harm your mt...

Sure, it is a great way to slow down in an emergency, but it is not something someone should be doing all the time IMO. Shifting in and out of gear in a MANUAL does no harm (if shifting correctly) but autos are a different story.


...i guess its just me ive always had mts and never once had a tranny or clutch prob and have always downshifted and any one who is true to the clutch will call you a noob if your just throwing it in n and slamming the brakes from 4th gear.. even autos downshift themselves its a good way to slow down your engine and your whole car and when done right will not cause any damage to your clutch flywheel or any other tranny component

Key words here: when done right. Judging only the areas I drive, most people dont know how to drive a stick right.

HeathenBrewing
01-24-2008, 03:28 PM
one last thing why would your foot be on the accelelerator while in neutral?

I dont know, but I never said that myself.

Nastos
01-24-2008, 03:29 PM
and if you are in gear and your foot is off the gas then you are effectivley downshifting and you just proved my point thank you and even if you are in gear and you have the clutch down thats the same as being in n

ok i see we were confused you were talking about autos and i was talking about m/t's lol sorry if i got a lil fiesty yeah an auto is made to drive its self not to be shifted while moving probably not so good for the trans lol

HeathenBrewing
01-24-2008, 03:36 PM
if you are in gear and your foot is off the gas then you are slowing down, but I wouldn’t say you were downshifting in a MT. Eventually your AT trans will downshift at some point, but not right away.


Go on with your fiesty self….debate is good and no offense was taken. But yeah, we keep going back and forth between the two transmissions. The original poster was speaking from an AT point of view, and I think that’s where we should be staying.


I contend that there will be no real MPG increase when shifting into N to coast with an AT.

Nastos
01-24-2008, 03:40 PM
i agree i dont think you should even touch the shifter in an at accept to park and drive and reverse from your parking spot lol at's are soo touchy and easy to ruin

tanakasan
01-24-2008, 04:30 PM
i agree i dont think you should even touch the shifter in an at accept to park and drive and reverse from your parking spot lol at's are soo touchy and easy to ruinHmm, I do manage to manually go into second at times and flick the OD on/off on long uphills/downhills.

AT is smart, but is still not perfect. So telling it to get out of OD should not kill it, IMHO. This is within the normal function range for the trans. Nor should shifting into second. BTW, you can yank the shifter into any gear you want at speed. The trans is smart enough to not go into a lower gear and cause an over revving condition. And there is a lockout to prevent accidental reverse...for most people.

If you were not supposed to ever manually shift that sucker, why did Toyota give you 3 selectable forward speeds and an OD button? Should just say "forward/reverse" and "drive now, stupid".

Just turned 30k, I will repost in another 30k. :P

bB2NER
01-24-2008, 04:53 PM
As long as the engine is still running the trans is still being lubed so it will not hurt the trans at all. I love coasting in my auto during long downhill sections. It will save gas because at idle you burn less fuel than you do in drive at 2K plus rpms.

dz302
01-24-2008, 04:53 PM
why don't you just keep your revs low??? or if your havent cleaned your fuel injectors lately try buying a bottle of cleaner and putting it in your tankTheir is significant engine braking with the automatic trans and I actually "lose" speed when I lift the throttle and leave it in drive. Therefore, on occasion I have placed it in neutral and when I do my scanguage registers significantly higher instant fuel mileage.

I don't know what you mean by keeping my revs low. I use high quality gasoline and I run Sea Foam in my tank every 4 tanks so I know my fuel system should be very clean.

dz302
01-24-2008, 04:56 PM
<<<if you wanted to coast around town you shoulda just opted for a manual they are generally a lil better on gas anyway>>

I don't coast around town, mainly down hills on highways and the Interstate. I purchased an automatic trans for reasons of not wishing to constantly shift gears, I suppose the same reason as everyone who purchases an automatic.

dz302
01-24-2008, 04:57 PM
Coasting in your box will NOT help mileage. Engines are a lot different in 2006 then they were in 1976 Read some more about VVTI and it will explain why coasting in N will not help you save gas.I will do some reading on VVTI. However, my scangauge shows the mileage go up substantially when I shift to neutral when going down hills.

dz302
01-24-2008, 05:01 PM
It is entirely possible the savings you are getting from doing this is coming from your desire to get better mileage. The VVTI turns the fuel delivery "off" when you lift your foot from the accelerator. It feeds more fuel to the fuel injectors with the trans in N than it does with your trans in gear and your foot off the gas.[/quote]

Interesting, then the only issue I have with lifting my foot off the throttle while still in drive when going down hills is that my car slows down, sometimes substantially. That doesn't do well when in traffic.

Maybe I need to just abandon the coasting theory...LOL

Thanks for the info.

Oh, can you link me to some sites about the VVTI??[/b]

tanakasan
01-24-2008, 07:04 PM
<<<if you wanted to coast around town you shoulda just opted for a manual they are generally a lil better on gas anyway>>

I don't coast around town, mainly down hills on highways and the Interstate. I purchased an automatic trans for reasons of not wishing to constantly shift gears, I suppose the same reason as everyone who purchases an automatic.And so that you're not turning 4k rpm at highway speeds! Less RPM = quieter and better mileage!

I coast my AT. There, I said it! :doh:

HeathenBrewing
01-24-2008, 08:46 PM
Oh, can you link me to some sites about the VVTI??[/b]

Id start with the "stickies" in the drivetrain section. Google it along with the engine name and you should find plenty of info.

I just printed out relevant info as I found it, so Idont have any direct links.

D_M_A_N
01-25-2008, 05:19 AM
:yawn: