Automatic Transmission Fluid - Ford 1999 Taurus Owner's Manual

Fluid level for power steering
Use only MERCON ATF power steering fluid.
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If the power steering fluid is low, do not drive your
vehicle for a long period of time before adding fluid.
This can damage the power steering pump.

Automatic Transmission Fluid

Under normal circumstances, you do not need to
check the fluid level of the transmission, since your
vehicle does not use up transmission fluid. Refer to
the Maintenance Schedule booklet for replacement
intervals. However, if the transmission is not
working properly — for instance, the transmission
may slip or shift slowly, or you may notice some
sign of fluid leakage — the fluid level should be
checked.
It is preferable to check the transmission fluid level
at normal operating temperature 150˚F-170˚F
(66˚C-77˚C), after approximately 20 miles (30 km)
of driving. However, if necessary, you can check
the fluid level without having to drive 20 miles
(30 km) to obtain a normal operating temperature if
outside temperatures are above 50˚F (10˚C).