What is the Shelf Life of Radiator Coolant or Antifreeze?

How long does radiator coolant last?

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Radiator coolant, sometimes called antifreeze, is the green, yellow, or orangish liquid that fills your car's radiator. The coolant in your radiator is a 50/50 mixture of commercial coolant and water, and together this solution makes a liquid that helps cool your engine by circulating through the cooling system. It also keeps your cooling system from freezing up in the winter. 

When you notice that the coolant level in your radiator is low, you may wonder if it's okay to use that jug of partially used coolant/ antifreeze sitting on your garage shelf. So just how long will that jug of antifreeze last before it goes bad? As it turns out, coolant/antifreeze will last a very, very long time. 

What Is in Coolant/Antifreeze?

The principle ingredient in commercial antifreeze/ coolant is either ethylene glycol or propylene glycol. It also may contain ingredients intended to keep the metal in your radiator from corroding. When mixed in a 50 percent coolant/water solution, this liquid has both a lower freezing point and a higher boiling point than water, meaning that it can function both as an antifreeze and coolant in your engine's cooling system. Antifreeze solution, in a proper mixture, will not freeze until air temperatures reach -35 degrees Fahrenheit, and will not boil until the solution reaches 223 degrees Fahrenheit. 

Does Antifreeze/Coolant Go Bad?

The chemical ingredients in antifreeze/coolant are quite stable and virtually never degrade. This means that the commercial product you've purchased can really sit your shelf almost indefinitely without ever going bad—provided, of course, that you keep the container sealed against dirt and other contaminants. There is no reason at all why you can't use a partial container to mix up additional solution to top off a radiator that's a little low on coolant. It's also not a problem to use an old jug of coolant/ antifreeze when it's time to flush and refill your radiator. 

Caution Regarding Disposal

Both ethylene glycol and propylene glycol are dangerous chemicals, and worst of all, they have a somewhat sweet taste that can make them appealing to children or pets. Always keep containers of antifreeze safely stored out of reach, and be careful not allow spills to remain on the ground where pets or wildlife might drink it.

Most states have prescribed methods for disposing of used antifreeze solution or unused containers of commercial coolant. It is illegal and unethical to dump antifreeze or coolant down the drain or pour it out onto the ground. Antifreeze can easily run off into rivers and streams or seep down through the soil into groundwater supplies. Instead, store old or leftover antifreeze in sealed containers with clear labeling and drop them off at an official recycling center. Some auto repair shops and dealerships may accept old antifreeze for reprocessing, sometimes for a small charge. In some communities, any retailer who sells antifreeze is required by law to also have procedures for processing old antifreeze. Recycling centers typically will send old antifreeze to processing centers that remove contaminants and reuse the active chemicals in new products.