Pontiac 1996 Grand Am Owner's Manual page 207

Adding only plain water
to
your cooling system
can be dangerous. 'Plain water, or some other
liquid like alcohol, can boil before the proper
coolant
mix'
will. Your vehicle's coolant warning
system is set for the proper coolant mix. With
plain water or the wroug mix,
your engine could
get too hot but you wouldn't get the overheat
warning. Your engine could catch.fire and you or
others could be burned. Use a 50150 mix of clean
water and DEX-COOL
TM
antifreeze.