Buick Enclave Owner's Manual page 276

The coolant recovery tank cap has
this symbol on it.
When the engine is cold, the coolant
level should be at or above the
FULL COLD line marked on the
recovery tank.
When the engine is hot, the level
could be higher than the FULL
COLD line. If the coolant is below
the FULL COLD line when the
engine is hot, there could be a leak
in the cooling system.
If the coolant is low, add the coolant
or take the vehicle to a dealer for
service.
You can be burned if you spill
coolant on hot engine parts.
Coolant contains ethylene glycol
and it will burn if the engine parts
are hot enough. Do not spill
coolant on a hot engine.
If coolant is needed, add the proper
DEX-COOL coolant mixture at the
coolant recovery tank.
Steam and scalding liquids from a
hot cooling system can blow out
and burn you badly. Never turn
the cap when the cooling system,
including the surge tank pressure
cap, is hot. Wait for the cooling
system and surge tank pressure
cap to cool.
If coolant is needed, add the proper
mixture directly to the radiator, but
be sure the cooling system is cool
before this is done.