Proper use of the over-drive system?

I have a 97 nissan infinity i 30(in the process of slowly restoring it) and one thing that has bugged me since I bought the car is: How am I supposed to use the over drive system? Like under what conditions is it useful?

I hear from some people that I should leave it on all the time to save on gas, but that doesn't sound right to me. It only really seems useful beyond 60 MPH. Checked around online and found nothing. Wondering if anyone here has had a similar system before and knows how to use it.

reply to post by korathin


I always leave mine on. The default setting is on in new cars.

Overdrive is a part of the automatic transmission that helps the torque converter (the part of your transmission that converts power from the engine into power the transmission can use) cool itself. When the transmission shifts into overdrive, the torque converter goes into what's called 'lock-up', meaning that it stops turning so it can cool itself and the transmission no longer is using it. When pulling heavy loads, traveling on rough terrain, or up steep inclines, turn your overdrive off, otherwise you could cause damage to the transmission! Otherwise leave it on. I does help your gas mileage on long trips, but then, cruise control does too. Be sure and have the fluids in your transmission changed every 30K or once a year if you live in a highly populated area with lots of traffic, otherwise every 50K or two years.

source

reply to post by korathin


who knows my crappy commodore has an over drive in it and i dont see the real difference if i drive it all the time on over drive or not, i guess all it would be doing is wearing out that gear... or ofcourse i have no idea what im talking about... over drive as a gear isnt the same to having that quick press the button over drive...

It increases your final drive ratio, generally the final drive is about 1:1, meaning the output from the gearbox is spinning at the same speed as your engine. Overdrive changes this ratio usually in the final drive (last gear) or the 2 top gears. This allows car when travelling at higher speeds to increase economy by having a higher final drive ratio as opposed to the engine, eg: engine 1:1.3 final drive.

Overdrive is not ideal for driving on ranges or up hills and around town and you want your engine to work less and have more torque.

Any other car stuff anyone wants to know about just ask

Originally posted by exo87
It increases your final drive ratio, generally the final drive is about 1:1, meaning the output from the gearbox is spinning at the same speed as your engine. Overdrive changes this ratio usually in the final drive (last gear) or the 2 top gears. This allows car when travelling at higher speeds to increase economy by having a higher final drive ratio as opposed to the engine, eg: engine 1:1.3 final drive.

Overdrive is not ideal for driving on ranges or up hills and around town and you want your engine to work less and have more torque.

Any other car stuff anyone wants to know about just ask

hi can i ask u this..a few years ago i was at work (uk) and a work m8 said he was getting this 4x4(cant remember)
but he said it had 12 cylinders and was at a nominal speed it would cut from 12 cylinders to 2 to save fuel, can u give me anymore info on that plz...thx in advance....regards dave

reply to post by davesmart


Sorry haven't heard of a 12 cylinder 4x4, but some vehicles do have the system you are speaking of where they deactivate cylinders. Take chryslers 300c for example, the hemi v8 in the 300c can "drop" 2 cylinders on each bank of the engine to reduce the fuel it uses under light load.

reply to post by Volund


tyvm! Also thanks to the other replies. After reading everything I guess it doesn't make any sense to leave it on as I normally only drive 10 miles to work, and like 7-13 miles if I have to go shopping or something.

always leave it on....only take it off if driving over very hilly conditions or if your pulling something

Originally posted by THEDUDE86
always leave it on....only take it off if driving over very hilly conditions or if your pulling something

Right! In most cases, the design engineers are smarter (and thus, the car) is smarter than you are.

Basiscally, it is just another gear in your transmission to save gas and unnecessary engine wear. Think of it that way.

If the drive to work rarely gets you above about 35mph, the overdrive may not engaged (even if on) at that speed. Or it may engaged anytime the transmission gets into its high range.

Originally posted by exo87
reply to post by davesmart

 

Sorry haven't heard of a 12 cylinder 4x4, but some vehicles do have the system you are speaking of where they deactivate cylinders. Take chryslers 300c for example, the hemi v8 in the 300c can "drop" 2 cylinders on each bank of the engine to reduce the fuel it uses under light load.

cheers m8 i remember now...dave

Note that 'overdrive' can be a loose term... Sometimes, that feature may be called a toggle between 'sport' and 'economical' modes.

I use over drive only beyond 60 kph speeds if lightly loaded and above 80 kph if loaded(e.g. carrying heav loads, towing, or climbing hill, racing). Above 100 kph if conditions warrant it.

If the car is loaded or if you need to constantly speed up and slow down such as in medium to heavy traffic, the transmission will shift more often with ovedrive engaged and will increase wear on transmission.

On the otherhand, leaving overdrive off at high speeds (above 100 kph) will cause unnecessary high revs and increase wear on the engine as well as increasing fuel consumption.

Turning overdrive off once lower speeds are attained will also improve engine braking.

I owed once a '89 Buick Regal with overdrive. According to the manual the overdrive was the "highest gear" and it bumped a little when it kicked in which was normal. So driving with or without overdrive made no difference except when towing. At lower speeds it kicked in when there was no acceleration at around 45 Mph at around 1300 Rpm. But I recommend to check your manual, the transmissions are not the same.

BTW The Buick had a 3,1 liter V6 engine and was a real fuel saver, I drove it with 24 Mpg. That's a better mileage than my previous car which was an Audi 2.6 V6 4-step automatic without overdrive (18 Mpg).

Originally posted by Regenstorm
BTW The Buick had a 3,1 liter V6 engine and was a real fuel saver, I drove it with 24 Mpg. That's a better mileage than my previous car which was an Audi 2.6 V6 4-step automatic without overdrive (18 Mpg).

I can't say, most modern 3 liter V6 I drove played around 24 mpg on both US and Japanese makes (Pontiac, Chevrolet, and Toyota).

The 'overdrive' button on my car, even though said overdrive, worked more like a toggle between sport and economy mode. The car would immediately upshift when overdrive is engaged regardless of speed. It will upshift even at speeds as slow as 20 kph so it made a difference. I would disengage overdrive when passing another vehicle at high speed.

On a lot of modern cars, they got rid of the overdrive button because of this kind of question coming up and people being confused. Thus D on the gear selector of these cars actually has overdrive, and to turn off overdrive you use L3. (My car is that way.) So it seems that unless you're towing or driving a lot of hills, it's best to leave it on. Saves gas, and the engine revs lower and is less noisy on highway trips.