Should the OverDrive be on or off in my Mitsu Galant?

[MaxDSP]

Theres an O/D button on the shifter, and when OD is off, a light comes up on the dashboard saying "O/D Off". If I push the button in, the light dissappears. What Ive always thought is that overdrive is mainly used for climbing hilly areas and such, and it should be kept off if your driving on flat surfaces.

Last week, while I was dropping my mom off at work, the RPM gauge showed 4,000 @ 75 MPH or so. I realized that OD was off, because the light was on. I pushed the button in and the RPM dropped to around 2500 at the same speed. (BTW, is it safe to do this while the cars in motion). What gives?

Also, what do the other gears do on cars? On my intrepid, I have a "3" and and "L" (i think), and when I put the gear into 3, the car accelerates and brakes erratically.

 

[mrCide]

its like.. gears 1 2 3 and 4.. heh

 

[iamme]

O/D on for normal driving. Heh, I posted this question a while back

 

[Ryan]

It would be "on"

 

[PsychoAndy]

you should have OD on, just because cruising steadily at 45 or highway speeds it brings fuel burn down as well as lowers engine RPM's (less wear). The only time I would lock out OD on my car is if i'm climibing mountains, cause you need to use higher RPM's and more of the powerband on a climb and to engine break on the way down so i dont boil my fluid.

-PAB

 

[BenRosey]

Definitely OD on for highway driving.

The rest of the time it's always been controversial in my mind. But I think leaving it on for city driving is good to go also. But the controversy is that it causes more wear since it's (in theory) always shifting to the next lowest gear when maybe it wouldn't have with OD off.

So leave it on...

 

[Thegonagle]

Stupid marketers have non-car people confused with the terminology, but it boils down to this: Overdrive, while the term does have a technical origin, is just another name for 4th gear on a 4 speed automatic transmission. In general, you want more gears. The warning light when the OD is off is there to remind you to turn it back on. What the light really means is "4th gear off."

Just like the automatic shifts while you're in motion, it is perfectly safe to push the button while in motion.

There should be more info in the owners manual, even though you, like 95% of drivers, probably won't read it.

 

[woodie1]

Most of the time overdrive should be used. If you are in a very hilly area or towing a trailer then you may want to turn it off.

Using it saves gas as well as wear on the engine by reducing the operating RPM.