Given Nitrogen atom is larger/heavier than O2...perhaps helps the car 
hug the road and corner better...   :-)

However, the theory is because its a larger moleculue it won't seep out 
as easy as that 21% that O2, retaining
optimum pressure longer...but this is unproven.  It's also suppose to 
lower the moisture content in the tire.
To keep this, it would mean that when the tire appears low you'd have to 
go to a dealer to have more nitrogen put in it,
as oppose to the corner station air pump....

http://www.straightdope.com/columns/read/2694/is-it-better-to-fill-your-tires-with-nitrogen-instead-of-air

Just another way to get into your wallet...

Newton, Ernie wrote:
>  
> Okay, I'm nearing 60 and I've never put anything in my tires except good 'ol
> gas station air.  (Not counting Fix-Flat now and again).
>
> What is the purpose of gasses other that oxygen?
>
> Ernie
>
> -----Original Message-----
> From: HP-3000 Systems Discussion [mailto:[log in to unmask]] On Behalf Of Fairchild, Craig D
> Sent: Friday, February 20, 2009 2:51 PM
> To: [log in to unmask]
> Subject: Re: [HP3000-L] OT: Are dealerships to blame for slow car sales?
>
>  
> ...
>   
>> Yup, the little
>> car had nitrogen filled tires (60.00),
>>     
> ...
>
> Wow, $60 for nitrogen filled tires. 
>
> I fill my car's tires with a special blend of about 78% nitrogen, 21% oxygen, and 1% of a blend of other gasses. That usually costs me about 25 cents.
>
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