JasonAndreas

The air you breath is 78% nitrogen and the nitrogen you get at Costco or any other tire shop is 95% nitrogen. The filters on the machines they use can't produce anything purer.

arrowax

I agree, we won't see the benefit of nitrogen with a road-car. "Race teams uses nitrogen because it expands in a more predictable manner (than air), so teams can better determine how tire pressure will increase during the race." Got it from the current C&D mag.

RayGT3

The coefficient of expansion of all gasses is about the same, extreme little difference. It all relates, again, to moisture content, not the kind of gas it is. You want dew points of -30 deg C or better. Air at this dew point is just as good or better than the "Nitrogen" they are selling. I don't think the dew point of the commercial offering is at the -30 level. It would be interesting to know what the dew point actually is in the tire store gas. I don't know if it would make any sense to ask what the dew point is, don't think they would know. They could be doing more harm than good if the Nitrogen was wet. Anyone know the specs of the gas they are selling?

Dry ------ Good
Wet ----- Bad

There seems to be a lot of magic attached to this. (Merchandising)