Used Coolant Antifreeze

Antifreeze is a water-based additive that lowers the freezing point of the water in your engine and prevents boiling in high temperatures. That’s why you may have also heard it called engine coolant, and why it’s important for your car year-round.

Manufacturers typically make antifreeze with either ethylene glycol or propylene glycol. The chemical base is significant because ethylene glycol is toxic if ingested and propylene glycol is “generally recognized as safe” by the Food and Drug Administration in low doses. If you have curious little ones in your household, it’s a good idea to use propylene glycol (often marketed as “nontoxic”) antifreeze instead of ethylene glycol. This is especially important because antifreeze often has a sweet taste that attracts kids and pets. (Editor’s note: “Nontoxic” propylene glycol antifreeze can still be toxic to children and pets, so please store it out of reach.)

There are also numerous colors of antifreeze — and the color matters. The most common color is green, but when buying antifreeze, you want to make sure you buy the correct color. Mixing colors can cause engine damage. Luckily, the color has no effect on the recycling market; it’s a dye that’s used for branding.