Increased fuel economy, based on the nitrogen filled tire staying at its optimal pressure longer than an air filled tire. But you'd have to really let your air filled tires be low for a while before you wasted $20 in gas. Yes, even at $4/gal.

IMO, a gimmick aimed at getting more $ from consumers. The green-washered valve-stemmed tires leak just as much as non-green ones, in my happenstance, casual, non-scientific observation over the years.

This so reminds me of Y2K garbage that came around. Of course any tech knew that that was only related the old 8-bit systems of which by then most had been replaced.
Lets look at this one. They claim that the O2 and moisture leach through the tires causing deterioration and loss of pressure. Beings how this is very little O2 to begin with one must concede that after you refill your tires the percentage of O2 that you are adding is so minimal, by volume, that it would not change the percent of nitrogen left over in the tire. That's if you buy the only O2 leaches out after that ylu have mostly nitrogen anyhow. Know onto the greatest source of info TV (lol)on the mythbusters show they tried breathing air from a tire under water and it did not work,know one bothered to check the amount of O2 in the tire but my guess is that is pretty close to pure nitrogen already, thus no help to a drowning guy. As far as moisture one summer in arizona and that's not a problem. Please understand that each are entitled to the own opinion just that the Y2K cast consumers a fortune and each time you turn around someone is trying to build a better mouse trap. Personally I never believe someone trying to sell me something or come up with a new way to take my hard earn cash.

I think the idea of saving weight with nitrogen vs air is a bit of a strech. How much does the air in a tire weigh? How much can nitrogen save? Can't be much.

It's a gimmick, pure and simple.

I would never pay $15 or $20 for it. And, even if they say they are putting nitrogen in your tires, would you be able to tell?

First, you've lost any benefit by paying the $15 up front. Then if you ever make a trip to replace any of that precious nitrogen, you've lost more money. Also, if you drive for a few days on low tires, waiting to get to the nitrogen shop, you've lost more money.

Race cars use nitrogen because they can control pressures to the .1 PSI with it, and purchased nitrogen is more pure than air, has no moisture and holds a pressure slightly better. Military and commercial aircraft use it to control pressures and reduce Oxygen in the wings, where all the fuel is stored.

But the standard car tire gauge is only accurate to about + or - 5%. Put good old fashion air in your tires, check the pressure regularly, and enjoy your car.

If nitrogen pressure remains more constant at various altitude extremes, then it's probably good for airplane tires...

If nitrogen in the tires can, for whatever reason, cut .001 second off the 1/4 mile time of one of John Force's funny cars, which can make the difference between a good or bad payday, then it's probably good for dragster tires.

However:

--Since I have yet to find the aluminum wheel that will actually hold pressure indefinitely--

--Putting innertubes in tires would make you look like a dweeb--

--My tires wear out faster than my underwear--

--and as noted above, putting nitrogen in tires that are already filled with air in the first place makes no sense to me---

the nitrogen store can keep their magic gas, I got better places to spend what little money I got!

The benefits I see is the dryness of the N2 and the lack of oxidation.
While N2 is a slightly bigger molecule than 02 or Argon, I don't see you leaking oxygen that quickly over time.
Also, expansion from heat will be about the same as 02. Basic gas rule, PV=nRT, doesn't matter the gas. Add in the compressibility factor and you have PV=znRT, z being dependent upon the gas but is has VERY little effect. Your tires are already at much different pressures. Even using the elaborate equations with coefficients of expansion, there is no discernable difference in respect to this conversation.
Same holds true for weight, not enough difference to contemplate.

I try not to fill my tires on hot humid days. Too much moisture.

Hum. Noticed this in the morning's paper.

http://www2.ljworld.com/news/2008/sep/29/use_nitrogen_tires_gaining_ground/

There was an increase in the use of rocks as pets some years ago as well.

+1

The moisture in compressed air is mostly attributable to poor compressor/airline setup and maintenance. When I was racing, I had my garage compressor set up so that that final drier almost never had moisture in it, and I had a dedicated air tank that I took to the track to fill my tires with. That tank NEVER was filled anywhere other than my garage, so if we ran out of air and I had to use another source, it went directly into the tires.

While my air was not quite as dry as a nitrogen tank's supply, it was pretty close and a LOT cheaper.

+1 +1 Which comes down to the possible lazy maintenance practices of the shops for air we frequent. Be cause I like to paint sometimes I have a oil and water separator and a dryer installed on my compressor, so I guess I was on the right track.

Interesting...on craigslist today

nitrogen for your trailer tires?