Ford 1996 Taurus Manual page 192

Driving
When to use j (Overdrive)
j (Overdrive) is the usual driving position for
an automatic overdrive transaxle. It works the
same way D (Drive) works, automatically
upshifting or downshifting as the vehicle speeds
or slows.
However, j (Overdrive) also shifts into a fourth
gear — an overdrive gear — when your vehicle
cruises at a consistent speed for any length of
time. This fourth gear will increase your fuel
economy when you travel at cruising speeds.
When to use D (Drive)
D (Drive) eliminates the excessive shifting
between third and fourth gears that your vehicle
sometimes does when you are traveling through
hilly terrain in j (Overdrive). It also provides
more engine braking than j (Overdrive) for
descending hills or city driving.
When to use 1 (First)
Use 1 (First) when added engine braking is
desired when descending steep hills.
The automatic transaxle will shift to the proper
gear to ascend any grade without any need to
shift to 1 (First).
Do not go faster than 38 mph (61 km/h) in this
gear. You can upshift from 1 (First) to D (Drive)
or from 1 (First) to j (Overdrive) at any speed.
P (Park)
Always come to a complete stop before you shift
into P (Park). Make sure that the gearshift is
securely latched in P (Park). This locks the
transaxle and prevents the front wheels from
rotating.
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