GMC 1994 Yukon Owner's Manual page 282

What to Use
Use a mixture of one-half clean wuter (preferably distilled) and one-half
antifreeze that meets "GM Specification 6038-M," which won't damage
aluminum parts. You can also use a recyc1e.d coolant conforming to "GM
Specification
6038-M" with a complete coolant flush and refill. If you use
this mixture, you don't need to add anything else.
I
NOTICE:
If you use an improper coolant mix, your engine could overheat
and be badly damaged. The repair cost wouldn't be covered by
your warranty. Too much water in the mix can freeze and crack
the engine, radiator, heater core and other parts.
Some conditions, such as air trapped in the cooling system, can affect the
coolant level in the radiator. Check the coolant level when the engine is cold
and follow the steps under "Adding Coolant" for the proper way to add
coolant.
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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