Overdrive on a Ford Focus

[BACR]

I though i knew what this was but after gettin an automatic ford focus i am confused!?!

When i press the O/D button on the gearshift knob it says on the dash "O/D Off". Now with my from what i can understand in the manual it says that without O/D (im guessing that means its off) it only uses gears 1 and 3, and it says this will be more economical...... HOW?

Please if someone knows can you explian.

Or even better if someone could scan in that page or the For Focus manual. In the spanish version its page 75.

Thanks