Ford 2003 Mustang Owner's Manual page 149

If you use a brake fluid that is not DOT 3,
you will cause permanent damage to your
brakes.
Do not let the reservoir for the master
cylinder run dry. This may cause the brakes
to fail.
WINDSHIELD WASHER FLUID
Checking and adding washer fluid
Check the washer fluid
whenever you stop for
fuel. The reservoir is
highlighted with a
symbol.
If the level is low, add
enough fluid to fill the
reservoir. In very cold
weather, do not fill the
reservoir all the way.
Do not put engine coolant in the container
for the windshield washer fluid.
Maintenance and care
149