Chevrolet 1998 Express Van Owner's Manual page 262

NOTICE:
I f you use an improper coolant mixture, your
engine could overheat and be badly damaged.
The repair cost wouldn't be covered by your
warranty. Too much water in the mixture can
freeze and crack the engine, radiator, heater core
and other parts.
If
you have to add coolant more than four times a year,
have your dealer check your cooling system.
NOTICE:
Checking Coolant
If you use the proper coolant, you don't have to
add extra inhibitors or additives which claim to
improve the system. These can be harmful.
When your engine is cold, the coolant level shoi
FULL COLD, or a little higher.
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