Ford 1998 Windstar Owner's Manual page 279

The brake fluid reservoir
If you use a brake fluid that is not DOT 3, you will
cause permanent damage to your brakes.
Add fluid if level is 0.30" or more below the MAX line.
Do not fill the reservoir above the MAX line.
If you find that the fluid level is excessively low — below the
seam or ridge on the outside of the plastic reservoir — have the
brake system inspected.
Do not let the reservoir for the master cylinder run dry.
This may cause the brakes to fail.
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