Coolant Doesn't Last Forever

Coolant Doesn’t Last Forever

The condition of the coolant can be checked periodically with test strips that change color in response to chemical changes in the coolant.


Most late-model vehicles specify a certain type of coolant. Most of these are long-life coolants are good for up to five years or 100,000 miles of service. Such coolants use proprietary OAT (organic acid technology) additives to protect the engine and cooling system against rust and corrosion.

The condition of the coolant can be checked periodically with test strips that change color in response to chemical changes in the coolant.

The color of the test strip tells you if the coolant is still good, borderline or needs to be replaced. Or, the coolant can simply be changed at the recommended service interval for preventive maintenance. Either way, the coolant eventually needs to be changed because it doesn’t last forever.

What type of replacement coolant should you recommend? The different coolant types, colors and specifications have created a lot of confusion among motorists as to which type of coolant they should use. The best advice here is to recommend a coolant that meets OEM specifications and is compatible with the type of coolant that is already in the vehicle.

“Universal” coolants that are compatible with all makes/all models can be used in any late-model application. But for customers who want an exact replacement coolant, there are products that are the same or equivalent to the OEM coolants, too.

General Motors has specified Dex-Cool orange antifreeze that meets GM spec 6277M since 1996. Chrysler has specified a Hybrid Organic Acid Technology (HOAT) formula coolant (also called “G05” coolant) that meets their MS9769 specification since 2001. Ford changed over to HOAT coolants in 2002, and requires a coolant that meets their WSS-M97B51-A1 spec. On some newer Ford trucks, however, they have switched over to an orange OAT coolant similar to Dex-Cool.

The Asian and European car makes also have their own coolant specifications and colors. Some aftermarket coolant suppliers now offer one formula for Asian cars and a different formula for European cars.

For 1980s and older domestic cars and trucks with copper/brass radiators, the traditional “green” formula coolant is still a good choice. The traditional green formula coolant has fast-acting corrosion inhibitors, but also a much shorter service life (typically 2 to 3 years or 30,000 miles). The green formula coolant is typically less expensive than the long-life coolants, but is not recommended for newer vehicles that require an OAT or OAT hybrid coolant.

All of these coolants use ethylene glycol as the main ingredient. When mixed in equal parts with water (50/50 mix), ethylene glycol provides freezing protection down to -34 degrees F, and boilover protection up to 265 degrees in a 15 PSI system.

Premixed (50/50) coolant is the easiest for consumers to use because it provides the correct balance of antifreeze and water. It also eliminates the potential for contaminating the cooling system with dissolved salts and minerals that are in ordinary tap water.

Customers who are changing their coolant may also need a chemical cleaner to flush their cooling system if the old coolant is full of rust or sediment, a cooling system sealer if the radiator, heater core or head gaskets are leaking coolant and a new thermostat if the engine has overheated (overheating often damages the thermostat). They may also need new radiator and heater hoses (and clamps), too.

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