Buick 2007 Rendezvous Owner's Manual page 390

So, it is not a good idea to top off your brake fluid.
Adding brake fluid will not correct a leak. If you add
fluid when your linings are worn, then you will 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.
CAUTION:
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If your vehicle has 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 on page 219.
390
What to Add
When you do need brake fluid, use only DOT-3
brake fluid. Use new brake fluid from a sealed
container only. See Recommended Fluids
and Lubricants on page 485.
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.
CAUTION:
{
With the wrong kind of fluid in the brake
system, the brakes may not work well, or
they may not even work at all. This could
cause a crash. Always use the proper
brake fluid.