The above two scenarios are great examples of who would benefit and who would not benefit from nitrogen tire fill. The average soccer mom that never checks the tire pressure probably goes many many months between visits to her local tire shop (where presumably they would check/refill as needed). This means she would probably lose less air between fill ups if her shop filled the tires up with nitrogen vs conventional air.
On the other hand, you have the average car enthusiast (like most of us on here), whom probably check their tire pressure routinely and keep them topped off all the time. Of course we're not going to benefit
that much from nitrogen fill
Exactly how much air loss is hard to say due to too many variables. We have to take into consideration that not every one on the road have pristine condition wheels (with a perfectly smooth inner surface for the tire bead to seal against); also lots of people are still rolling around with rubber valve stems (which often might not seal as perfectly as TPMS valve stems), etc.
For example on my older vehicles, which have had dozens of tire changes, I've noticed the inner surface where the tire bead seals against is either corroded a bit or gummed up with rubbery stuff (from previous tire beads?), or both. This is clearly not going to seal as well as the brand new wheels on my 4runner.
I would imagine on a less than ideal tire/wheel combo, nitrogen would leak out noticeably slower than regular air; whereas on a pristine tire/wheel combo, you really can't tell the difference since well...if it ain't leaking much conventional air to begin with, how the heck can you tell how much less nitrogen leaks, lol.
This is just hearsay, but my dad has commented about how his tires leak a lot less now since costco started using nitrogen to fill his tires. His wheels are cheapo stamped steel with over 15 years of tire changing and rust. Coincidence or not? You be the judge.
