The modern "extended life" antifreezes, usually a color other than green, have an "organic additive technology" type of corrosion inhibitor package. These should be avoided at all costs in our older cars with brass/solder radiators, heater cores, etc. You'll find quite a bit on this topic in other posts probably here but also on the PAC Forum. See for example
packardclub.org/forum/viewtopic.php?f=10 ... id=62b32ee23844b6604bfa914c68634f15 The "good old stuff" like green Prestone uses a different corrosion inhibitor package which better suits our older cars. BUT the corrosion inhibitors don't last forever; they are consumed in the process of doing their job. Probably two or three years at most is all we should expect from them. So change your antifreeze every 2 or 3 years. The antifreeze won't loose it anti-freeze protection per se, it's the corrosion inhibitors that are depleted.
What I was referring to in that post is storing of radiators as spare parts with coolant in them. The same thing applies.
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