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Cool It (Again)

New Standards for Light- and Heavy-Duty
Recycled Engine Coolants

by René Weibe

Engine coolant (antifreeze) recycling is a relatively new and developing industry. New ASTM specifications have been developed for both light- and heavy-duty recycled engine coolants and recently have been released and implemented. These specifications provide minimum performance requirements for recycled engine coolants intended for use in both light-duty (passenger car and light truck), and heavy-duty (truck and off-road) applications. These specifications are meant to provide protection to vehicle owners and provide standards that can be used by original equipment manufacturers (OEMs), service and maintenance facilities, and government regulating agencies to specify coolant quality.

A Young Industry

The engine coolant recycling industry got its start in the late 1980s for several reasons. As a result of the federal government passing regulations that classified significant amounts of the used engine coolant as hazardous materials—materials containing lead levels greater than 5.0 ppm—many equipment and vehicle maintenance facilities sought ways to reduce hazardous waste costs while preserving our natural environment. This demand to reduce hazardous wastes and related costs created opportunities for many different companies and groups to develop and market effective means to recycle used engine coolants. Since ethylene and propylene glycol are economically recoverable components in engine coolants, many different ways were developed to separate out the contaminants from the ethylene or propylene glycol. The various processes included simple filtration, ultra-filtration, chemical precipitation and filtration, reverse osmosis, ion-exchange, and distillation.

As the young market developed without industry standards, it was necessary for processes to be refined and optimized to remain competitive in the industry. Several technologies developed clearly were producing inexpensive and poor quality recycled engine coolants while others provided higher quality recycled engine coolants. This led to significant, and understandable, concern from OEMs and state regulatory bodies. This concern drove a request into ASTM Committee D15 on Engine Coolants, which was asked to develop recycled engine coolant specifications for light and heavy-duty service. In response to this request, the D15.15 Recycled Coolants subcommittee was formed and charged with the task of developing recycled engine coolant standards.

While ASTM was in the process of developing industry consensus standards, OEMs such as General Motors, Ford, Chrysler, Caterpillar, and Cummins developed proprietary standards in response to the demand of the field. After developing these standards, they issued company- or process-specific approvals. Testing and approval programs varied in intensity, however; they were primarily based around virgin engine coolant requirements.

Standards for Light Duty Recycled Coolants

Within ASTM D15.15 meetings, the highly debated question of where to draw the minimum specification lines for light-duty recycled coolants were resolved through significant amounts of testing and benchmarking against test methods and specifications designed for virgin engine coolants. In addition, much of this work was compared to the large used coolant characterization database that was developed between 1989 and 1996, resulting in a good understanding of what inhibitor and contaminant levels are actually seen in the field. Since recycled engine coolants can contain constituents not normally found in virgin coolants, batteries of contaminant effect level testing were completed to determine whether chemical limits were needed or if existing virgin engine coolant requirements would suffice. It was finally determined that a performance specification with a synthetic used coolant recycle protocol and chemical hinge limits to determine performance requirements was the only way to get a consensus standard developed. Consensus was reached and the light-duty recycled engine coolant specifications were introduced in May 2000. These specifications are:

D 6471, Specification for Recycled Prediluted Aqueous Glycol Base Engine Coolant (50 Volume % Minimum) for Automobile and Light-Duty Service, and
D 6472, Specification for Recycled Glycol Base Engine Coolant Concentrate for Automobile and Light-Duty Service.

The light-duty recycled engine coolant standards that were developed do not place any restrictions on the type of recycling process. They do, however, have variable performance requirements. These requirements are hinged on the chloride and sulfate levels remaining in the recycled engine coolant after recycling a standard synthetic used coolant that contains 200 ppm chloride and 300 ppm sulfate. The synthetic used coolant is one that represents a worse-case engine coolant typically found in light-duty vehicles.

For recycling processes that can meet the chloride and sulfate hinge limits, performance requirements remain similar to those of virgin engine coolants. For those recycling processes that cannot remove chloride and sulfate below the hinge limits, fleet testing is required to validate the recycled engine coolant’s effectiveness to protect engine cooling systems from corrosion. The fleet test protocol requires a minimum of 10 vehicles to finish the test: five filled with recycled test coolant and five filled with a reference virgin coolant. The duration of the fleet test is one year, 48,280 km (30,000 miles) minimum, and 4,828 km (3,000 miles) per month maximum. At the end of the fleet test, the cooling system components from the vehicles containing the recycled test coolant are compared with those containing the reference virgin coolant. Additionally, metal specimens from each cooling system are evaluated for weight loss due to corrosion. This comparison style fleet test was set up for a couple of reasons. It allows for flexibility in the vehicles that can be used. Secondly, having reference test vehicles provides a baseline that reduces if not eliminates a lot of the variables pertaining to driving conditions and vehicle designs.

Standards for Heavy Duty Recycled Coolants

With respect to heavy-duty recycled engine coolant specifications, virgin engine coolant specifications were revised to include recycled engine coolants since it is necessary for both of these coolants to be similar in nature and have low initial total dissolved solids levels. As a result, this narrows down the types of processes that can be used to recycle heavy-duty engine coolants.

The reason for this is that heavy-duty engine coolants require the addition of supplemental corrosion inhibitors (that contribute to total dissolved solids) at regular maintenance intervals until the engine coolant is beyond its ability to adequately protect the cooling system and total dissolved solid contents reach solubility limits. This is quite different from light-duty engine coolant applications where the coolant is simply exchanged at its predetermined service interval. Heavy-duty cooling systems typically contain 38 to 57 liters (10 to 15 gallons) of prediluted engine coolant versus 4.7 to 11.4 liters (5 to 12 quarts) in most light-duty applications. Changing the engine coolant in heavy-duty engines at intervals specified for light-duty applications is neither needed nor practical if properly maintained. Heavy-duty engine coolant lives are extended with the previously mentioned supplemental coolant additives to minimize the amount of engine coolant that is needed to service heavy-duty engines, and to reduce the amount of time the vehicle/ equipment is being serviced. Additionally, it is not a simple process to change the coolant in heavy-duty engines. Two heavy-duty virgin/recycled engine coolant specifications were introduced in 1998. Both contain performance and chemical requirements:

D 6210, Specification for Fully-Formulated Ethylene-Glycol-Base Engine Coolant for Heavy-Duty Engines, and
D 6211, Specification for Fully-Formulated Propylene-Glycol-Base Engine Coolant for Heavy-Duty Engines.

The development and implementation of the new recycled engine coolant specifications is the beginning of refining, honing, and adding credibility for producers of high quality recycled engine coolants. As a result of the implementation, users of the specifications will not have to generate their own standards and can rely on the ones developed by an industry consensus organization. The need for proprietary standards is greatly diminished and allows for engine coolant recyclers to produce recycled engine coolants to a common standard rather than to each user’s specific requirements. For those that recycle engine coolants or use recycled engine coolants, these standards are the mark to hit when it comes to producing or specifying a good quality recycled engine coolant. //

Copyright 2000, ASTM

René Wiebe is the laboratory manager for Wynn Oil Company, Azusa, Calif., and serves as chairman of the ASTM D15.15 Recycled (Engine) Coolants Subcommittee. Wiebe is also a member of the Society of Automotive Engineers and the Society of Tribologists and Lubrication Engineers.