http://www.chicagotribune.com/business/autocorner/chi-mxa0727nitrogenjul27,0,907521.storyFree air same as fee nitrogen as long as your tires are properly inflated
By Bob Weber | Special to the Tribune
1:53 PM CDT, July 24, 2008
What started as a fad just a few years ago has ballooned into a profitmaker for tire dealers and a head scratcher for tire buyers: nitrogen inflation.
Nitrogen is colorless, odorless, safe and ubiquitous. Nearly 80 percent of the air we breathe is nitrogen. Unlike air, which contains oxygen, nitrogen won't support combustion so it has been used in critical situations for years: In aircraft tires, including Air Force One and the Space Shuttle. The military uses it in many vehicles as does NASCAR.
But is it worth up to $40 to inflate your car's tires with it?
Perhaps the biggest benefit from nitrogen is that its larger molecules are less likely to pass through the rubber than oxygen molecules. Yes, rubber is permeable. Think about that helium filled balloon that clung to the ceiling yesterday, but fell to the floor overnight. According to the Get Nitrogen Institute, with 95 percent nitrogen in your tires, they retain optimal pressure three to four times longer.
Four times longer than what? Air? Oxygen? Frozen custard?