What is the difference between blue and green antifreeze?

Answer 1

There could be no difference, or every difference. The color of an anti-freeze is no indication of its chemical makeup, it's only a dye added to make spotting leaks easier.

You'll have to read your owner's manual to determine if it is safe to use various types of coolants, as using the wrong coolant can destroy your engine.

For instance, if you have a small scooter or motorcycle engine that uses certain types of gaskets, and you use coolant that contains 2-ethylhexanoic acid (also known as sodium 2-ethyl hexanoate), the coolant can literally dissolve your gaskets, causing coolant to leak into the combustion chamber or into the oil. And unless you catch it right away, the engine will be destroyed.

Another instance, if your water pump mechanical seals are not designed to handle silicate-based coolants (usually the plain old ethylene glycol or propylene glycol coolants), the silicates can destroy the water pump mechanical seals, leading to coolant leaks. Again, if the low coolant level isn't caught right away, the engine will be destroyed.

Another instance, if you have an older coolant system that isn't perfectly air-tight (usually the older systems without an expansion tank to catch coolant overflow), as the coolant expands as it is heated, it will push some of the coolant out of the radiator. When it then cools and contracts, it will suck in some air. If you're using the new Organic Acid Technology coolants (usually potassium 2-ethyl hexanoate or sodium 2-ethyl hexanoate containing coolants), the air will react with the coolant, causing it to sludge up and plug your coolant passages. Again, if this isn't caught right away, it can destroy your engine.

So your best bet is to figure out what metals are in your system (and the metals can include magnesium, aluminum, low-lead solder, high-lead solder, copper, mild steel, cast iron), then research which chemicals are best for protecting those metals:

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Aluminum corrosion is best inhibited by silicate and most poorly by phosphate and borate.

Cast aluminum corrosion is best inhibited by silicate and most poorly by phosphate and molybdate.

Copper corrosion is best inhibited by molybdate and most poorly by benzoate.

High-lead solder corrosion is best inhibited by molybdate and phosphate and most poorly by nitrate, silicate and benzoate.

Low-lead solder corrosion is best inhibited by tolytriazole and molybdate and most poorly by nitrate and silicate.

Mild steel corrosion is best inhibited by molybdate, phosphate and nitrite and most poorly by tolytriazole and benzoate.

Gray cast iron corrosion is best inhibited by nitrate and most poorly by benzoate, tolytriazole, and borate.

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Then you need to figure out if your water pump mechanical seals can handle silicate-based coolant if you have aluminum in your system.