GMC Sierra Denali Owner's Manual page 294

What to Use
Use a mixture of one-half dean, drinkable water and
one-half DEX-COOL@ coolant which won't damage
aluminum parts. If you use this coolant mixture,
vou don't need to add anvthing else.
I
Addir
-
m i - -)lain water to lr cooling
s-
tem
can be dangerous. Plain water, or some other
liquid such as alcohol, can boil before the
proper coolant mixture will. Your vehicle's
coolant warning system is set for the proper
coolant mixture. With plain water or the wrong
mixture, 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 50/50 mixture of clean, drinkable
water and DEX-COOL@ coolant.
Notice: If 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: 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.
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