For nearly a decade, vehicle manufacturers have been introducing and using a variety of extended-life coolants. The only thing these coolants have in common is that they all seem to differ in formulation and color. There are orange coolants, green coolants, blue coolants, red coolants, yellow coolants, even pink ones. The proliferation of different coolant types has created a great deal of “chemical confusion” with motorists and technicians about what type of antifreeze should be used to top off or refill late-model cooling systems.

We’re not going to summarize the whole laundry list of OEM coolants and colors here except to say that each vehicle manufacturer has their own unique coolant specifications based on corrosion protection requirements, service life and chemical compatibility. These requirements are usually spelled out in the vehicle’s owner’s manual, and/or a decal or label on the coolant reservoir. It’s important to always use the coolant chemistry recommended in the vehicle owner’s manual. For example, Ford and Chrysler specify hybrid OAT-only coolants.

You can’t go by the color of the dye in the coolant because two coolants with similar colors may have different chemistry, and two coolants with different colors may have similar chemistry. What’s more, colors can change if somebody tops off the system with a different coolant.

The more we get into the specifics of each type of coolant, the more confusing the whole discussion becomes – so we’re only going to tell you what’s really worth knowing with respect to the different types of antifreeze.

There are essentially three basic types of coolants:

Traditional North American “green” antifreeze, the original “universal” formula that everybody used until the introduction of today’s extended-life coolants. The fast-acting silicate and phosphate corrosion inhibitors provide quick protection for bare iron and aluminum surfaces, and have a proven track record of providing trouble-free service in virtually any vehicle application (domestic, Asian or European), assuming the chemistry is correct. For example, OAT coolants should not be used in a vehicle that specifies the use of a hybrid OAT coolant. Again, always defer to the owner’s manual. But the short-lived nature of the corrosion inhibitors means this type of coolant should be changed every two to three years or 30,000 miles (though some products now claim a service interval of up to 50,000 miles with improved chemistry).

OAT-based extended-life coolants. OAT stands for Organic Acid Technology, and includes such ingredients as sebacate, 2-ethylhexanoic acid (2-EHA) and other organic acids, but no silicates or phosphates (except in the case of Toyota’s pink extended-life coolant, which adds a dose of phosphate to its extended-life OAT-based antifreeze). OAT-based coolants are usually, but not always, dyed a different color to distinguish them from traditional North American green antifreeze. GM’s OAT-based Dex-Cool is orange. Volkswagen/Audi uses a similar product that’s dyed pink. But Honda has an extended-life OAT coolant that is dyed dark green and does not contain 2-EHA.

The corrosion inhibitors in OAT coolants are slower acting, but much longer-lived than those in traditional North American green coolants. Consequently, OAT coolants typically have a recommended service life of five years or 150,000 miles.

OAT corrosion inhibitors provide excellent long-term protection for aluminum and cast iron, but may not be the best choice for older cooling systems that have copper/brass radiators and heater cores. It depends on the formula.

Hybrid OAT coolants, also known as “G-05.” This formulation also uses organic acids, but not 2-EHA (different organic acids are used). Hybrid OAT coolants add some silicate to provide quick-acting protection for aluminum surfaces. Silicate also helps repair surface erosion caused by cavitation in the water pump. Hybrid OAT coolants are currently used by many European vehicle manufacturers as well as Ford and Chrysler.

Still Confused?
OK, so there are a bunch of different coolants in today’s vehicles. The question is, which type of coolant should you recommend to top off or refill a customer’s vehicle?

The “safe” answer is the type specified by the vehicle manufacturer. But practically speaking, shops don’t have the shelf space to stock different coolants for each different make of vehicle.

One thing the aftermarket has always been good at is consolidation, and today’s coolants leave plenty of room for that. Recently, many antifreeze suppliers have introduced “universal” or “global” one-size-fits-all coolants that are claimed to be compatible with any new vehicle cooling system as well as older vehicles.

The basic idea behind universal coolants is to eliminate all the confusion about colors and chemistry and have one basic product that works in any vehicle regardless of year, make or model. What could be simpler?

Not all antifreeze suppliers buy into this marketing philosophy, so you’ll still see the three basic types of coolant being marketed: traditional green for older vehicles and budget-conscious motorists who want the least expensive product on the shelf, an extended-life product that is compatible with Dex-Cool and other OAT-based coolants, and a hybrid OAT for late-model Ford, Chrysler and European vehicles that specify G-05 coolant.

But for those who offer a universal “all makes and all models” kind of product, the advantages are obvious: one or two SKUs to provide full coverage (full-strength antifreeze or 50/50 mix), less shelf space needed to stock the product, and most importantly, no confusion over which product to use in which application.

Makers of universal coolants say their products are formulated to be compatible with all cooling systems (foreign or domestic) and all coolant types (traditional green, OAT and OAT-hybrid with silicate).

The new universal coolants use unique OAT-based corrosion packages with proprietary organic acids (such as carboxylate) to provide broad spectrum protection.

When a universal coolant is used to top off a cooling system that already contains an extended-life OAT or hybrid coolant, the service life is unaffected. It remains five years or 150,000 miles. If a universal coolant is added to an older vehicle that has traditional green antifreeze in the cooling system, the service interval is also the same as before: two to three years or 30,000 to 50,000 miles.

If a cooling system is being refilled with a universal coolant, the cooling system should be flushed to remove all traces of the old coolant. This is necessary to remove contaminants and to maximize the service life of the new coolant. If only the radiator is drained, up to a third of the old coolant can remain in the block.

If the old coolant is traditional green coolant, the new universal coolant will be diluted and won’t be able to extend protection much beyond that of the original coolant.

One very important point to keep in mind here is that universal coolants and extended-life coolants are not lifetime coolants. The corrosion inhibitors in all types of coolant eventually wear out and must be replenished by changing the coolant. Leave the old coolant in too long and the cooling system will experience corrosion problems.