Chevrolet 1994 Astro Passenger Owner's Manual page 251

To Check Brake Fluid
You can check the
brake fluid without
taking off the cap. Just
look at the windows
on the brake fluid
reservoir.
The fluid levels should be above
MIN.
If they aren't, have your brake
system checked to see if there is a leak.
After work is done on the brake hydraulic system, make sure the levels are
above MIN and below the top of each window.
What to Add
When you do need brake fluid, use only DOT-3 brake fluid - such as
Delco Supreme II@ (GM P a r t
No.1052535). Use new brake fluid from a
sealed container only, and always clean the brake fluid reservoir cap before
removing it.
NOTICE:
Don't let someone put in the wrong kind of fluid. For
example, just a few drops of mineral-based oil, such
as
engine
oil, in your brake system can damage brake system parts so
badly that they'll have to be replaced.
Brake fluid can damage paint, so be careful not to spill brake
fluid on your vehicle. If you do, wash it off immediately. See
"Appearance Care" in the Index.