Ford Grand Marquis Owner's Manual page 214

If you use a brake fluid that is not DOT
3, you will cause permanent damage to
your brakes.
Do not fill the reservoir above the MAX line.
The brake fluid reservoir
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.
RWARNING
RWARNING
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