OK -

The other answer is exactly correct for using the OD. The auto tranny OD system is set up so that when starting the car it is in OD, no arrow.

Actually the OD is not engaged on starting, the control over engagement is with the tranny, not the driver.

Engagement usually can happen when the car is on flat road and traveling at 40mph or more. Watch the tachometer for a 20% drop in engine speed when you feel the OD engage. Example: if your engine speed is 3000 rpm, when the OD engages look for a drop to 2400 rpm. Not exact, but close.

When the amber "Up" arrow is on, the control is inhibited so the tranny is inhibited from shifting into OD. It stays in 3rd gear, and at the higher revs the engine has more power - good for passing or towing.

OD is named that because it is a gear set that causes the drive shaft to rotate over the engine speed. That allows the engine to rotate slower while keeping the same road speed. Works only when the drop in engine power output at the lower rpm is of no importance because the extra power is not needed.

Hope this helps.

Regards,

Bob

:>)