More than likely it is the old green (high silicate) antifreeze which should not be used in any cooling system since 1994. Read the manual in your glove compartment in the specifications pages for the long-life chemical antifreeze part number at the dealer of the car.
High silicate green antifreeze will damage aluminum engine parts.
I don't know if it "loses it potency" over time, on the shelf.
However, I would find it hard to believe that antifreeze manufactured at 20 year old standards could have any chance at all of protecting a modern engine against such things as corrosion, elctrolysis etc...
Might be OK at basic freeze protection though.
First best answer to Mike. 20 year old antifreeze is what we now think of as "conventional green" coolant, something that still works in 20 year old cars. Most modern vehicles use special formulations, most low in silicates or no silicates (the old stuff is loaded with silicates), low/no borates, low/no amines..... If you have a car from the 1980s or earlier it should be okay. Anything newer, go with the proper coolant.
They are just fine, for use in an antique car or tractor!
However I totally agree with Mike that 20 year old Anti-Freeze simply is not made to the specifications which modern engines require and would not therefore use it in any modern car or truck.
No, it does not loose it's potency. The additives in it will not be correct for new cooling systems, though.
i found store-bought, unopened containers of antifreeze in my father's garage and I know they've been there for 20 years or more and wondered if they are still any good.
