Over-drive

What does this little button in your car mean and should it be on or off?

[pokerdirty]

I hear cars get the best gas mileage when you drive in "2"

[ QUOTE ]
I hear cars get the best gas mileage when you drive in "2"

[/ QUOTE ]

<sigh>
Silly man... it's when you drive in reverse.

My dad is a mechanic, and Ive asked him before, and I believe he said keep it on most of the time, unless the speed limit is 35, and you hover between 35 and 40, then the gear shifts too much. It doesnt do much damage, but its a pain in the ass.

[eviljeff]

having over-drive on is kind of like being in a higher gear. so if you turn over-drive off while stopped, you'll have better acceleration initially, but your top speed will be greater with over-drive on once you're going.

edit: I'd just leave it on the whole time unless you have specific advice to do otherwise.

[swede123]

There are two times when you should turn off the overdrive:

1) When towing a load that's a bit more than the vehicle can handle comfortably you might notice the car shifting from 4th gear (assuming a 5 speed tranny) to overdrive and back again. In this case it's better to just leave it in 4th and drive a bit slower.

2) When going down a long hill you might turn off overdrive, letting the engine do some breaking for you. This saves the brakes from wearing out so fast, and if it's a real nasty hill it might prevent the brakes from overheating and losing their power.

Swede

[The Goober]

[ QUOTE ]
having over-drive on is kind of like being in a higher gear. so if you turn over-drive off while stopped, you'll have better acceleration initially, but your top speed will be greater with over-drive on once you're going.

edit: I'd just leave it on the whole time unless you have specific advice to do otherwise.

[/ QUOTE ]

This is utterly incorrect.

Overdrive just means "enable 4th gear" - when its on, the car can shift into 4th if its in 3rd already and feels like upshifting. With it off, the car will never shift past 3rd (and will downshift if you turn it off while in 4th gear).

You will probably never need to turn it off - you will waste a lot of gas and put a lot of extra wear on your engine if you do any amount of of highway driving with it off.

It's amazing how widely misunderstood this button is. When I bought my old car a long time ago I asked the dealer what it did. He made up something and clearly had no idea. I looked it up in the owner's manual later and was shocked at how dumb that dude was (I mean, he sells these things for a living...).

edit: swede explained better why you would turn it off. Also, I assumed a 4-speed auto - for a 5-speed just change 4th to 5th and 3rd to 4th