From the Christian Science Monitor on October 17, 2008:
Whether or not it makes environmental sense to inflate car tires with nitrogen instead of air is a matter of much debate. Proponents of nitrogen say it is a smart choice primarily because it leaks from tires at a slower rate than air, so tires stay fully inflated longer. That, in turn, helps a vehicle attain better gas mileage. According to the Get Nitrogen Institute, a Denver-based nonprofit that advocates replacing the air in our tires with nitrogen, underinflated tires are a big contributor to global warming, as they cause drivers to waste fuel.
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