What do all the different colors of antifreeze mean and what should I be using?

In the past, most antifreezes were green. Now, manufacturers use a variety of colors in their antifreeze product lines. Green generally, but not necessarily, indicates an automotive or light duty formulation. Orange antifreeze generally means extended-life type of antifreeze. It is ethylene glycol-based like most green antifreezes but contains different corrosion inhibitors.

The various manufacturers use colors to identify their products in a bit of marketing gamesmanship; however, there are no hard rules governing the use of these colors. Equipment manufacturers and consumers should have an ability to identify their approved fluid. In addition, color has been used in antifreezes as a safety measure to discourage accidental ingestion.

Since the mid-1990’s, the proliferation of coolant colors has caused considerable confusion. All engine coolants use a glycol base but include different performance additives that inhibit (control) scale/ corrosion. Believe it or not, all of these coolants are clear, water white before dye is added.

The traditional green coolant is based on inorganic additives and is called inorganic additive technology (IAT). It is a tried and proven chemistry that provides a fast acting protective film. The additives deplete, though, and need to be replenished every couple of years.

Fully formulated engine coolants were developed in response to user demands for a simpler, universal, longer life coolant technology. Heavy-duty operators had to use low silicate automotive coolant formulations (high silicate automotive antifreezes could cause “green goo” in diesel engines) that required a separate SCA additive. This often resulted in mixing errors when the SCA was added at initial fill or when topping-off. Unlike automotive antifreeze, fully formulated coolants are pre-charged with SCA’s and contain all of the ingredients necessary to protect diesel, gasoline, and gaseous fuel engines. Pink has become recognized as the color for fully formulated coolant, although they are also commercially available in green (as required by government agencies). These products meet performance requirements for major automotive specifications, allowing mixed-fleet operators to stock one antifreeze formula for all of their vehicles.

A new type of antifreeze, referred to as extended or long life, has emerged. Its unique chemistry differs significantly from that used in traditional antifreezes. Referred to as organic acid technology (OAT), this new chemistry uses organic acids to protect cooling system metals. Extended life antifreezes have been colored red or orange depending on the supplier; however, more colors may be used in the future. While these fluids do not deplete during service, they also do not protect as quickly as IAT coolants. These differences require a significant change in procedures used to maintain the cooling system.

General Motors® has been using this technology (DEX-COOL®) in their cars and trucks since 1996. They use an orange dye for DEX-COOL® product. A Ford Motor Company® study concluded that OAT coolants “do not offer any significant advantages for the consumer…” and “…current coolant corrosion protection can be extended far beyond previous expectations”. Cummins Engine Company announced in a memo dated July 16,1999, that OAT coolants are not compatible with their engines. Cummins is reporting that these long life antifreezes cause degradation of silicone seals in their engines after 80,000 to 100,000 miles of service. Cummins, therefore, is not recommending the use of OAT coolants in their engines.

Hybrid organic acid technology (HOAT) uses both inorganic and organic acid additives for long life protection. The objective with HOAT is to provide excellent all around protection and extended drain intervals. HOAT coolants generally can replace or are compatible with green IAT in older vehicles. Chrysler used conventional green IAT coolant until 2001, when they adopted G-05®, a hybrid coolant. Ford followed suit in 2002, dropping the green IAT for G-05® factory fill and extending the drain interval. Variations of HOAT coolants have been around for more than 50 years.