Ford 1996 Windstar Manual page 340

The power steering fluid cap
If the power steering fluid is low, add fluid in small
5.
amounts, continuously checking the level, until the fluid is
between the minimum (MIN) and maximum (MAX) lines on
the dipstick. Do not overfill.
Make sure the cap is free of all dirt prior to re-installing to
6.
prevent pump damage.
Use only power steering fluid that meets Ford Specification
ESW-M2C33-F, such as Ford Premium Power Steering Fluid,
E6AZ-19582-AA or an equivalent Type F Automatic Transaxle
Fluid with a Ford registration number (an 8-digit number
beginning with "2P" printed on the fluid container).
NOTE: 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.
If you must check the power steering fluid when it is cold,
make sure that the fluid reaches at least the minimum (MIN)
mark. The reading will only be accurate if the fluid temperature
is approximately 70˚ to 100˚F (21˚ to 38˚C).
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