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Photo of antifreeze being poured into a car

Antifreeze is a substance added to a solvent, such as water, to lower its freezing point. Antifreeze is typically added to water in the cooling system of an internal-combustion engine so that it can be cooled below the freezing point of pure water (32 degrees F) without freezing. Ethylene glycol is the most widely used automotive cooling-system antifreeze, although methanol, ethanol, isopropyl alcohol, and propylene glycol are also used. In automotive windshield-washer fluids, an alcohol (e.g., methanol) is usually added to keep the mixture from freezing; it also acts as a solvent to help clean the glass. The brine used in some commercial refrigeration systems is an antifreeze mixture; it is typically a water solution of calcium chloride or propylene glycol.

Antifreeze is toxic to humans and animals. Waste antifreeze contains heavy metals such as lead, cadmium, and chromium in high enough levels to potentially make it a regulated hazardous waste, so most states strictly regulate antifreeze disposal. Antifreeze generators and state and local programs should not dump spent antifreeze on land or discharge it into a sanitary sewer, storm drain, ditch, dry well, or septic system; dumping antifreeze can cause serious water quality problems and might harm people, pets, or wildlife.

Just the Facts

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Recycling Used Antifreeze

Recycling used antifreeze makes sense for two reasons: 1) It is cost-effective, and 2) It saves resources. Ethylene glycol, the primary active ingredient in antifreeze, is produced from natural gas, which is a finite, non-renewable resource. For businesses that use a lot of antifreeze, like automobile repair shops, setting up an antifreeze recycling program can significantly reduce management costs and lessen the amount of new materials purchased. Using new technology, these businesses are recycling antifreeze on site and reconditioning it with additives at a cost that is significantly lower than the cost of purchasing new antifreeze.

Antifreeze recycling involves two steps:

  1. Removing contaminants such as emulsified oils and heavy metals either by filtration, distillation, reverse osmosis, or ion exchange.
  2. Restoring critical antifreeze properties with additives. Additives typically contain chemicals that raise and stabilize pH, inhibit rust and corrosion, reduce water scaling, and slow the breakdown of ethylene glycol.

New technology lets generators of spent antifreeze recycle antifreeze on site by removing contaminants and reconditioning it with additives, at a cost that is significantly lower than the cost of purchasing new antifreeze. Another option for recycling antifreeze includes power flushing the radiator, restoring the coolant, and topping off the vehicle with fresh coolant in a closed loop. Recycling saves resources since a primary ingredient, ethylene glycol, is produced from natural gas, a non-renewable resource.

To find a location to recycle your antifreeze, please visit Earth 911 Exit EPA.

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Extended-Life Antifreeze

Conventional antifreeze lasts only two or three years, as the chemicals that slow down antifreeze corrosion are depleted. New extended-life coolants represent a major advancement over conventional coolant technology and greatly reduce the need to purchase new and manage used antifreeze. Different chemicals in the antifreeze made with extended-life coolants allow it to last five years or 150,000 miles. Heavy-duty, extended-life antifreeze lasts between 400,000 and 600,000 miles with the use of a one-time extender. Manufacturers expect that over the coming years, this technology will replace conventional antifreeze and become the industry standard.

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Alternative Ingredients for Antifreeze

Antifreeze typically contains ethylene glycol as its active ingredient, but some manufacturers market propylene glycol-based antifreeze, which is less toxic to humans and pets. The acute, or short-term, toxicity of propylene glycol, especially in humans, is substantially lower than that of ethylene glycol. Regardless of which active ingredient the spent antifreeze contains, heavy metals contaminate the antifreeze during service. When contaminated, particularly with lead, used antifreeze can be considered hazardous and should be reused, recycled, or disposed of properly.

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Recommendations and Standards

See ASTM D6471 and D6472 Exit EPA.

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