[todd92]

Must be a lot of people that didn't pay attention during high school chemistry. N2 does not expand or contract any different than air. It does not leak out more slowly. Boyle's Law PV=nRT. The only logic behind using N2 is it is dry, it has no water vapor. This might prevent corrosion and when dropping below freezing keeps the water vapor from condensing, which would appear as a pressure drop. Most air compressors have a drier, to keep the water out of air tools, so this really makes using N2 pointless.