In Reply to: what I learned about antifreeze posted by ButtonRock on October 13, 2018 at 03:29:35:
Though the freeze protection properties of so-called "permanent anti-freeze" last indefinitely, the corrosion protection properties do not. Correspondingly, coolant should be changed every two years or so, depending upon conditions/usage.
Additionally, as Tim mentioned, it is important to get all of the old coolant out when changing. Simply opening the radiator drain cock will usually drain only about 1/2 of the coolant. If your engine has a block drain (most do not these days) you should open it as well.
Once the old coolant has been removed, you can flush with clean water and re-drain. Do not use commercial radiator flush chemicals unless you want to replace your water pump within a short while.
When refilling, refill with new, concentrated anti-freeze and distilled water. I avoid premixed anti-freeze because I have not found any that say that distilled water rather than tap water is used in the mix.