overdrive

This is a question specifically for the 99 elantra, but I guess most people
using overdrive will be able to answer it.. do you guys leave your overdrive
on all the time or off? Or do you just use overdrive when you are driving at
high speeds (eg. on the interstates etc)? And what is overdrive exactly? Is
it like the 5th gear in a manual trans?? My friend told me to leave it on
all the time, as that will give me better fuel consumption (but less
acceleration).. is that true?

 

The OD button enables/disables 4th gear. With it turned off you will
have better acceleration +35mph but higher fuel consumption.

 

I leave it on all the time on all my vehicles, except when travelling
through the mountains on steep grades (up or down). (Hyundai, Chrysler &
Fords)
Yes, like 5th on a manual.

 

But it seems to impact overall acceleration, so I almost wonder whether it
is like a 2 speed set of gears that are in-line with the other, gears so
that you are either in the steeper "overdrive" or the lower "non-overdrive"
setup.

 

The only time it will hamper your acceleration is if the vehicle refuses to
downshift into third. There is no second set of gears. The button simply
enables and disables 4th gear. With O/D off, it would be comparable to
driving a 5spd manual without the option of shifting to 5th.

 

Interesting. Around town, from a standing start or even while moving slowly
the vehicle seems to accelerate less rapidly with the OD button activated...
almost like it at least has a different shift profile or something.

 

That's possible. It may move the shift points higher as well. That's
one of the things that the "Sport" button in Saturn vehicles did (as
well as disable 4th gear).