I’d have to agree with this being a lot of misleading hype. The roughly 22% Oxygen that is in the air that we breath is only 3% smaller than the Nitrogen molecules which make up 78% of our air. One would be hard pressed to believe that this ever so slight difference would make ones tires prone to under inflation. Another fact is that most air compressors used to fill ones tires have air dryer than the surrounding air we breath. (inline dryer or dessicant). My final conclusion, waste of money. Check your tires often and put the money wasted on nitrogen into some good gas. Having the nitrogen may actually give a person a false sense of security believing that they need not check their tires as often… Food for thought. Matt
Welcome to the SDMB, Matt.
A link to the column you’re commenting on is appreciated. Providing one can be as simple as pasting the URL into your post, being sure to leave a blank space on either side of it. Like so: Is it better to fill your tires with nitrogen instead of air? - The Straight Dope
Some previous threads on this:
Nitrogen for Tires
nitrogen in tires error!
Filling Your Tires With Nitrogen
Is filling tires with nitrogen a gimmick?
nitrogen-inflated tyres?
I don’t diagree at all with your final conclusion, but permeation of gasses through polymers depends on more than gas molecule size. I looked this up a while ago. For natural rubber, permeation rates are 4.8X10[sup]12[/sup] molecules/(seccmatm) for O[sub]2[/sub], 1.75X10[sup]12[/sup] molecules/(seccmatm) for N[sub]2[/sub], and (for comparison) 6.3X10[sup]12[/sup] molecules/(seccmatm) for He. So oxygen will, indeed, permeate faster than nitrogen, and measurably so.
However, in practice, it seems to me that the effect on tire inflation of pure nitrogen v. an 80/20 mixture would be negligible, particularly if you either a) check your tire pressure every so often and refill as needed, or b) have a slow leak.