[HandyDandy]

Suppose I were to say "pure nitrogen"? Would that make it a little bit true? As Moltke kindly pointed out to me (post#18) it is the fact that pure nitrogen is a dry gas that makes it stable under pressure. Unlike any gas that might be contaminated with water. Yes, there are other dry gases but nitrogen is the go-to for NASCAR, IndyCar, NASA, the military, airlines, etc.

http://www.getnitrogen.org/sub.php?view=nascar

If the NFL used pure nitrogen as the gas to fill their footballs with, would your statement still be true:

"So the natural variation in pressure of footballs in NFL games from temperature alone is nearly 6 PSI."

[Moltke]

The calculation is made for an “ideal gas”, so it’s the best case scenario. Yes, the statement would still be true.

[lepton]

If the NFL used pure nitrogen as the gas to fill their footballs with, would your statement still be true:

“So the natural variation in pressure of footballs in NFL games from temperature alone is nearly 6 PSI.”

---

Yes.

The effects of water vapor condensing are additional.

The main reasons for using Nitrogen in NASCAR are chemical. Nitrogen is chemically relatively inert to each metals and oils/lubricants compared to water and oxygen - especially when hot.