On Mar 1, 2:04*pm, WindsorFox > wrote:

> Jan Andersson wrote:
>
>> Esteban wrote:
>>
>>> Hi folks, quick question for the folks in the know. *Yesterday I took
>>> the wife's 05 Mustang in for the 30,000 mile check up. *The service
>>> writer asked me if I wanted nitrogen in the tires, the cost would be
>>> $32.50. *With all due respect to myself, I ain't no rocket scientist. *
>>> I know about and why they use nitrogen in aircraft tires...but, why
>>> would anyone pay extra to have nitrogen in auto tires.
>>> Please, someone help me understand this.
>>> Thanks,
>>> Steve
>
>> To slow down the aging of the rubber?
>
> * * Larger molecules, don't leak out. Way too extremely expensive IMHO..

October 04, 2007
Tires - Nitrogen air loss study

Filling tires with nitrogen rather than air is becoming a common
practice in the replacement tire market. This service offers tire
dealers another avenue for making money while also promoting safety.
The claimed safety benefits often include the potential for reducing
air loss compared to an air-filled tire. Maintaining proper inflation
can help prevent tire overheating; promote optimum tread life; and
reduce rubber aging and wheel corrosion. The use of nitrogen in large
truck fleets and the commercial tire industry are well documented and
support these claims.

The National Highway Traffic Safety Administration (NHTSA) has seen
reduced aging of tires filled with nitrogen. Though the data does
support that passenger car tires could benefit by all the claims made
for nitrogen, tire manufacturers say that they already design tires to
perform well with air inflation. And while nitrogen will do no harm,
manufacturers say that they don't see the need to use nitrogen, which
generally adds $5 or more per tire charge.

Consumer Reports wanted to find out if nitrogen is worth the price, so
we purchased a Nitrogen Inflation System and checked out how well the
inflation held up over a one year period. We evaluated pairs of 31
tire models of H- and V-speed rated, all-season tires used in our
tread wear test from 2006. We filled one tire per model with air and
the other with nitrogen. The test was quite simple: fill and set the
inflation pressure at room temperature to 30 psi (pounds per square
inch); set the tire outdoors for one year; and then recheck the
inflation pressure at room temperature after a one year period.

The tires were filled and deflated three times with nitrogen to purge
the air out of the tire cavity. We also used an oxygen analyzer to be
sure we had 95-percent nitrogen purity in the tire--the claimed purity
limit of our nitrogen system, which generates nitrogen gas from
ambient air.

The test started on September 20, 2006 and the final measurements were
taken on September 20, 2007. The results show nitrogen does reduce
pressure loss over time, but the reduction is only a 1.3 psi
difference from air-filled tires. The average loss of air-filled tires
was just 3.5 psi from the initial 30 pressure setting. Nitrogen-filled
tires lost an average of 2.2 psi from the initial 30 psi setting. More
important, all tires lost air pressure regardless of the inflation
medium, so consumers should check their tires' air pressure routinely.
No evaluation was done to assess the aging claim.

Bottom line: Overall, consumers can use nitrogen and might enjoy the
slight improvement in air retention provided, but it's not a
substitute for regular inflation checks.

http://blogs.consumerreports.org/car...nitrogen-.html

Moreover, since nitrogen is supposedly less prone to volume change
with heat change many new car dealers' service departments routinely
substitute nitrogen for compressed air when their customers Tire
Pressure Monitoring System (TPMS)-equipped vehicles come in during the
colder winter months complaining about their TPMS warnings.