How to Dispose of Antifreeze

Changing your car’s radiator fluid (aka, coolant or antifreeze) is an important part of preparing it for the extremes of weather—be it very hot or very cold. This blog entry discusses the hows & whys, including the way to dispose of spent antifreeze properly. Q&As include:

1. What is antifreeze?

2. Why can’t pure water be used as an engine coolant?

3. Why is radiator coolant called antifreeze?

4. Why does antifreeze need to be changed?

5. How often does “antifreeze” need to be changed?

6. Is antifreeze toxic?

7. How to get rid of antifreeze?

8. How does old antifreeze become tainted?

9. Can you pour antifreeze down the drain?

10. Can you recycle antifreeze?

11. How do you transport old antifreeze?

12. Where can you get the best advice about disposing of antifreeze?

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1. What is antifreeze?

Actually, “antifreeze” is a misnomer. This is because what’s commonly called antifreeze is actually a coolant that courses through special passages in your car’s engine block to keep it from overheating. Remember, no matter the year’s season, a car engine without radiator coolant will overheat to complete destruction in short order. 

Radiator coolant keeps the engine’s temperature within safe limits (190° F to 225° F) by absorbing heat via conduction (see source). The absorbed heat then gets “radiated” into the atmosphere as the coolant gets passed through—you guessed it—your car’s radiator, which lives under the hood and (usually) in front of the engine (see source).

The radiator coolant also journeys through a heat exchanger, a little radiator beneath your dashboard that warms you by having an electric fan blow across it. Your car’s temperature control regulates how much hot coolant passes through the heat exchanger: a lot in the winter, none in the summer, and something in between for spring and fall.

2. Why can’t pure water be used as an engine coolant?

In fact, pure water was used in the earliest internal combustion engines. But water freezes at 32° F and boils at 212° F. If it freezes, it will expand and crack the engine block. If it boils, it can no longer absorb heat. 

Today’s auto engines operate at temperatures that render pure water useless as a radiator fluid. Thus, modern radiator coolant is formulated to have a boiling point of 387° F and a freezing point of -37° F, well beyond the extremes of temperature that your car is likely to produce or encounter. 

3. Why is radiator coolant called antifreeze?

If the coolant in your car’s engine were to freeze in the winter, it would expand enough to crack open the engine block, meaning it would be new-car time. To prevent this catastrophic event, radiator coolant is formulated to have a freezing point of -37° F, safely below any wintery temperature your car might encounter. Ergo, radiator coolant is often referred to as “antifreeze” so antifreeze coolant.

4. Why does “antifreeze” need to be changed?

Radiator coolant (aka, antifreeze) will deteriorate over time, and become less resistant to freezing or boiling. Also, engines have many parts that can rust. The radiator coolant will pick up this rust as it circulates through the engine block, depositing it in places where it can wreak all sorts of expensive damage. Regular flushing keeps the coolant clean and prevents blockages (see source).

5. How often does “antifreeze” need to be changed?

Depending on the vehicle and the coolant, the recommended time between flushes is two years or 30,000 miles for “silicate coolants,” and it’s up to five years or 100,000 miles for “extended drain coolants.” You can determine which you have by its antifreeze color.  

• Silicate coolants are fluorescent green. The silicate raises the boiling point, lowers the freezing point, and coats your engine parts to inhibit corrosion (see source). 
• Extended-life coolants are orange. They contain organic acids that deplete much more slowly than traditional coolant additives (see source).

6. Is antifreeze toxic?

The main ingredient in antifreeze (aka, radiator coolant) is usually ethylene glycol (aka, ethane). It’s an organic compound that’s odorless, colorless, flammable, and viscous. Unfortunately, it’s also toxic. Along with raising the boiling and lowering the freezing point of the coolant, ethylene glycol acts as a lubricant and anti-corrosive agent (see source).

[Some types of coolant use propylene glycol instead of ethylene glycol, which is less toxic but should be handled with care like toxic waste (see source)].  

We should add here that ethylene glycol has a sweet taste. And while it might not occur to you to use it as a cocktail mixer, dogs—on the other hand—think it’s simply delicious. They’ll happily lap up any that spills or leaks onto a garage floor or driveway; and even a tiny amount can be highly poisonous. Just a half-teaspoon per pound of Fifi’s body weight can be fatal (see source); and bear in mind that a single liquid cup contains 32 half-teaspoons. 

Given this danger, you need to absorb spilled radiator coolant ASAP. Use baking soda or kitty litter to soak up as much as possible. Then, cover the affected area with paper towels. After a couple of hours, toss the paper towels into a sealable plastic garbage bag and place it into your normal trash stream. Finally, squirt liquid soap on the affected area, scrub it with a sponge or scouring pad and then rinse it with water. Fifi would thank you—if only she knew.

7. How to get rid of antifreeze?

You should never dump spent antifreeze onto the ground or down a drain (see Q. 8). Doing so would allow ethylene glycol to seep into the nearby soils and groundwater, which could pollute water sources, kill flora, sicken fauna, and make the EPA very, very unhappy. (N.B. It’s a bad idea to make the EPA very, very unhappy.)

The best solution is to take old antifreeze to a service station or auto repair shop that accepts spent coolants and motor oils for disposal. However, you must determine whether your antifreeze is tainted rather than merely old (see Q.8). 

8. How does old antifreeze become tainted?

Radiator coolant (aka, antifreeze) can become tainted with heavy metals secondary to rust in your engine. Or, if your engine has a damaged head gasket, the coolant might be polluted with oil or gasoline. In either case, the tainted coolant is considered a RCRA hazardous waste. So, your local service station or auto repair shop will be loath to take it off your hands. Instead, you’ll have to contact an appropriate facility or hire a properly “permitted” waste hauler to transport the antifreeze to a licensed coolant disposal facility. It’s here where we generally advise: get expert advice. 

9. Can you pour antifreeze down the drain?

In most of America, antifreeze (aka, coolant) cannot be poured down any drain, no matter if that drain leads to a private septic system or a municipal sewer. However, some municipalities allow coolant to be poured down a drain if it’s diluted, and the drain leads to the municipal sewer—not a septic system. Go figure. (See example).

10. Can you recycle antifreeze?

Not if it’s tainted (see Q. 8). But if it’s merely old, check your state’s waste management website for guidelines for antifreeze recycling or disposing of geriatric coolant (aka, old antifreeze). If you come up empty there, try contacting your local recycling center or a local government office (your call is important to them). The aforementioned automotive repair shops might also be of help. After you try all that, opt to get expert advice. 

11. How do you transport old antifreeze?

You should transport old radiator coolant (aka, antifreeze) in sealed, plastic containers that are well secured in your car trunk or pickup bed. Label each container with the date, the brand of coolant, and the coolant’s chemical disposal contents (if you know it). If your antifreeze is tainted with gas, oil, or heavy metals, indicate that on the label, too. As we’ve mentioned before, only pure antifreeze can be recycled. Tainted antifreeze must be managed as a hazardous waste (see Q.8).

12. Where can you get the best advice about disposing of antifreeze?

We thought you’d never ask! You need an environmental services partner with a documented history of providing safe, efficient, and compliant waste and radiator fluid disposal guidance. Hazardous Waste Experts is that company specializing in waste management and disposal. We’re a nationally recognized, premier source of advice and expertise concerning the management and disposal of automotive coolants, motor oils, gasoline, or any other noxious substances—liquid or solid—that are considered RCRA wastes.