Can Red and Green Antifreeze Be Mixed?
2 Answers
Red and green antifreeze cannot be mixed, as they differ in type, composition, and freezing point. Mixing them can cause chemical reactions that reduce the antifreeze's effectiveness, produce flocculent substances leading to clogging of the cooling system, and in severe cases, corrode the engine's water passages and cooling pipes. Functions of antifreeze: 1. It has anti-corrosion and rust-removal properties; 2. Its high boiling point prevents the radiator from boiling over; 3. Made with distilled water, antifreeze also helps remove scale. The chemical components of antifreeze include: inorganic calcium chloride (CaCl2), organic methanol (CH3OH), ethanol (C2H5OH), ethylene glycol (C2H4O2), erythritol, glycerol (C3H5(OH)3), glycerin, lubricating oil, sugar, and honey.
Last time I saw this situation at the repair shop, someone mixed red and green antifreeze, resulting in lots of foam in the radiator. The mechanic said antifreeze of different colors may have conflicting chemical compositions—red is usually ethylene glycol-based while green might be propylene glycol-based. Mixing them can deactivate the corrosion inhibitors, leading to crystal formation that clogs the engine's water passages. In summer, this can cause overheating, and in winter, it might freeze and crack the radiator. Nowadays, automotive antifreeze typically lasts about five years. When topping up, it's best to use the same brand and color. If unavailable, adding distilled water temporarily is better than mixing randomly. If you've already mixed them, rush to flush the cooling system—don't hesitate to spend that hundred or so bucks on new antifreeze. Repairing the engine would cost way more.
