FWIW, I just saw this on the Prestone web page:

Q: Does Prestone antifreeze/coolant contain phosphates?
A: Some European automobile manufacturers request that a
phosphate-free antifreeze be used in their vehicles. This issue is
related to the extremely high mineral content of the water in Europe.
If you were to mix an antifreeze that contained phosphates with the
type of water they have in Europe, it may produce deposits that can
settle in the cooling system and promote corrosion.

However, in North America we do not have this type of water problem.
Typical North American coolants have contained phosphates (which is
part of the corrosion inhibitor package) for many years. Therefore,
the question of phosphates is a non-issue here in North America.
Prestoner antifreeze/coolant is completely safe for use in both
foreign and domestic vehicles.

For those consumers who would feel more comfortable using a
phosphate-free antifreeze, our Prestoner Extended Life 5/150 is
phosphate, silicate, and borate free. This coolant uses a special
chemistry and technology that extends the life of the corrosion
inhibitor package so that it lasts for five years or 150,000 miles
(whichever comes first), and is safe for all cars and light trucks
(old or new).

-Karl
Regards,

-Karl

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