Buick REGAL 1997 Manual page 305

There are only two reasons why the brake fluid level in the
reservoir might go down. The first is that the brake fluid
goes down to an acceptable level during normal brake
lining wear. When new linings are put in, the fluid level
goes back up. The other reason is that fluid is leaking out
of the brake system. If it is, you should have your brake
system fixed, since a leak means that sooner or later your
brakes won't work well, or won't work at all.
So,
it
isn't a good idea to "top off' your brake fluid.
Adding brake fluid won't correct a leak. If you add fluid
when your linings are worn, then you'll have too much
fluid when you get new brake linings. You should add
(or remove) brake fluid, as necessary, only when work is
done on the brake hydraulic system.
If you have too much brake fluid, it can spill
on the engine. The fluid will burn if the engine
is hot enough. You or others could be burned,
and your vehicle could be damaged. Add brake
fluid only when work is done on the brake
hydraulic system.
When your brake fluid falls to a low level, your brake
warning light will come on. See "Brake System Warning
Light" in the Index.
What to Add
When you do need brake fluid, use only DOT-3
brake fluid
--
such as Delco Supreme 11
@
(GM Part
No. 12377967). Use new brake fluid from a sealed
container only.
Always clean the brake fluid reservoir cap and the area
around the cap before removing it. This will help keep
dirt from entering the reservoir.
1
CAUTIC
With the wrong kind of fluid in your brake
system, your brakes may not work well, or they
may not even work at all. This could cause a
crash. Always use the proper brake fluid.