Ford Mustang Owner's Manual page 219

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 — 3.8L engines
The brake fluid reservoir — 4.6L engines
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.
R WARNING
221