Inhibited Water Coolants for use in Warm Climates
An engine cooling system always needs water
50% Antifreeze is always the standard recommendation, but treated (inhibited) water is used in some situations.
Water with some high quality inhibitor turns pink because it contains a pH indicator (phenolphthalein) to signal that all is well. When the color fades, it might need more inhibitor!
Although almost every vehicle manufacturer recommends glycol-based antifreeze at 50% in water for the primary coolant requirement, some permit the use of inhibited water in areas and situations where the engine will never be subjected to temperatures below 32 degrees F (0 degrees C).
Water is a better heat transfer fluid than glycol, and obviously it is far less expensive and it is also less toxic.
In general most inhibitors used in water based coolants are liquids. There do exist some powders and pellets, but the majority are liquids. Mixing liquid to liquid is much easier than powders. Most additives designed for this type of application comply with ASTM D5952, a good performance specification that requires an additive to protect the cooling system when only water is used. Most of the time additives are used at 3%-6% in water. Check with the additive manufacturer for specific recommendations
Using water provides optimum heat transfer. Water-based coolants are often used in Southern California, Arizona, and Florida. They are also very common in tropical countries and in marine vessels.
Water based coolants need to be maintained just like antifreeze-containing coolants. The inhibitors can age and wear, and need to be bolstered from time to time.
In general, thy should be checked with an appropriate (additive manufacturer recommended) test strip every month, 20,000 miles or 300 hours, whichever comes first. The additive concentration should be maintained according to the additive and / or engine manufacturer's recommendations.
This type of coolant is most commonly chosen for use in large equipment that never travels far from home, and that needs large volumes of coolant. Examples are power generation systems and mining equipment.
