Originally Posted by OKC-XFR
Regular atmospheric air is 78% nitrogen, 21% oxygen and 1% argon -- so when you fill up at a pump or with your compressor, you're putting in over 3/4 nitrogen. There are claims that pure nitrogen is more stable, but I don't see how that extra 22% would make that much of a difference.
If what you read about nitrogen is true, then:
When the tire leaks, it should leak primarily oxygen and not Nitrogen, leaving a higher % of nitrogen. You refil with normal air, leaving the oxygen % lower than it was originally. Over time, The % of oxygen would get smaller and smaller
if oxygen is more prone to leakage than nitrogen.