You could use the overdrive all the time, it cuts down on fuel consumption, with no major noticeable effect on power.
If you choose to keep it off... You will need to turn it on when cruising above 40-45 MPH, it's actually the higher gear on the Automatic Transmission, very similar to 5th gear on stick shift.
all the time
You have to use it when you are driving in mountain areas where to have high speed is not a good idea. The overdrive function does allow the transmission to switch to higher gears.
Yes
It's not recommended to use overdrive on a constant base. It stresses too much the engine as well as transmission.
not recommended overdrive is for cruising at highway speed
No. Overdrive should be turned off when towing any trailer.
In simple terms, overdrive is the final/cruising gear. It reduces the power output by lowering the gear ratio. The overdrive mechanism increases fuel efficiency, and saves strain on the transmission and the drive train. When the vehicle is started the overdrive is always on, but it can be turned off by a switch button, which is often located on the shifter. Turning the overdrive off will prevent the vehicle from shifting into the overdrive when traveling at the speed of around 40 MPH. It is recommended that the overdrive is constantly on under normal driving conditions. It should be turned off when, for example, hauling heavy loads or going up a long gradual incline.
Overdrive is the normal position - if you are in hilly areas and find the transmission keeps shifting back and forth between overdrive and drive , you can use the overdrive cancel switch to shut off the overdrive feature and if you are towing something you also want to shut off the overdrive
Toyota does not use inertia/reset switches.
When you are not towing during highway use.
Overdrive is the normally allowed position It won't shift into overdrive until the speed is higher anyway ( such as on the highway / freeway ) If you are towing something , or are driving in hilly country where the transmission is constantly shifting between overdrive and drive , you want to switch the overdrive off using the switch on the end of your gear selector lever ( P R N etcetera , the O/D OFF light will appear in your dash )
I believe overdrive should automatically be enabled on any car. Overdrive allows a car to drive at fast speeds with low engine input (low revs) resulting in better gas mileage. The downside is that you lose torque. You should be able to turn it off for things like climbing mountains and using engine breaking to go down them. Unless you turn it off, it's already on.