Mercury Sable 1999 Owner's Manual page 108

Driving
N (Neutral)
With the gearshift in
P R N D D 1
the N (Neutral)
position, the vehicle
can be started and is
free to roll. Hold the
brake pedal down while
in this position.
(Overdrive)
The (Overdrive)
P R N D D 1
position is the normal
driving position for an
automatic overdrive
transaxle. It works the
same way as D (Drive)
but shifts to a fourth
gear — an overdrive
gear — when your
vehicle cruises at a
constant speed for any
length of time. This
fourth gear will
increase your fuel economy when you travel at
cruising speeds.
Overdrive may not be appropriate for certain
terrains. If the transaxle shifts back and forth
between third and fourth gears while you are driving
hilly roads or if your vehicle requires additional
power for climbing hills, shift into D (Drive).
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