1994 GMC Suburban Owner's Manual - Page 282

What toUse 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 arecyc1e.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 can freeze and crack mix the engine, radiator, heater core and other parts. Some conditions,such as air trappedin 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 additiveswhich claim to improve the system. These can be harmful. 6-36