Supposed to preserve the inside of the tire, by eliminating the reactive O2, among other benefits.
more consistent pressure, less dryrot etc., but i've read the nitrogen costs next to nothing and it's a huge moneymaker for those that charge for it. some places don't charge for it if you buy tires from them, even if you need to refill later on etc.
i think the same critic said they understood charging something for the service, but that it shouldn't be more than $2-3/tire and anything much more than that he felt the cost far outweighed the benefits
And even at that, you have to wonder how many tires are retired from use due to dry rot, rather than worn out treads or other structural problems?
I've even heard the claim that N2-filled tires are safer, cause they don't have O2 to burn in case of a fire! Given the ready supply of O2 in the atmosphere, the last thing I'm gonna worry about in case of a fire is whether my tires will be supplying any of the O2. :yes: