Yes, you can fill ’em up with ordinary air, which is cheaper and more widely available. Air is 78 percent nitrogen, so by refilling the tires with regular air you’re just diluting the nitrogen content, which was originally probably around 95 percent. The key benefit of nitrogen is that it permeates out of tires at a slower rate than oxygen, which is 21 percent of air, so in theory you shouldn’t have to check or fill your tires more often.
The bigger benefit, however, may be for those who sell it. The Get Nitrogen Institute (www.getnitrogen.org) says nitrogen usually goes for $3 to $10 per tire. You can pump a lot of ordinary air for that money, and you should check your tires at least monthly for inflation pressure and to see if there is any damage.
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