You really shouldn't be messing with this very dangerous stuff in the
first place. Use stable oils like coconut or palm kernel. Now, to
answer your question: let's say you've got high quality olive oil,
rich in antioxidants. Then you pour it into this container that has a
trace of the old rancid oil in it. The amount of the rancid oil will
be taken care of by the antioxidant rich olive oil. The problem is
that low quality olive oil, for example, doesn't need help from this
trace amount - it's ready to go rancid very quickly once exposed to
air. If you keep the jar closed, and use one of those stoppers that
can be vacuum sealed, it will not go rancid. However, this stuff will
go rancid inside your body, unless you eat a very antioxidant rich
meal. So again, why mess with this stuff to begin with?