Coolant shelf life?

[NLR]

I found a gallon jug of BMW coolant in my garage left over from when I did a coolant flush almost three years ago. I had previously opened it to top off my coolant a while back. I'm planning on doing a coolant flush today and was wondering if there is such a thing as coolant going bad after some time even if it is still in the original container? I would like to know ASAP so that if need be I can make the trip to get more if the one I have is unusable. Also, I can't remember exactly how many jugs of coolant I used last time. Assuming I go with the recommended 50/50 mixture, how many gallons will I need? TIA

[fisherbln]

I'm not sure about the shelf life, but, you will need about 3 gallons of 50/50 mixture after flushing.

[thejlevie]

Coolant expires as a result of depletion of the oxygen getters it contains. I'd be hesitant to try to use a partially container that old as it may not provide full corrosion protection. A couple of gallons of fresh anti-freeze doesn't cost all that much and it is sure to properly protect the engine.

While one can dilute antifreeze with ordinary tap water, that is full of dissolved oxygent and may contain other disolved minerals. For just a few bucks you can use distilled water, which contains hardly any oxygen and no disolved minerals.

[Daved]

I always put new coolant when I flush it, I don't use left-overs. It's not that expensive, better be on the safe side.

[NLR]

Thanks guys! New coolant it is then.