Save Gas with Nitrogen Filled Tires?

I bought a red Pontiac G6 that came with bright green tire valve caps. They were ugly so I put them on my daughter's bike - she thinks they're cool. The green valve caps are used to indicate that a vehicle’s tires are filled with Nitrogen as opposed to compressed air.
Companies that sell and promote Nitrogen systems note several benefits to filling your tires with Nitrogen. Among them are:
1.Nitrogen is a larger molecule than CO2 so there is less seepage or incremental loss of pressure over time;
2.Nitrogen helps keep the tire cooler; and
3.Nitrogen does not expand and over-inflate the tires as compressed air does after driving a few miles.
All of these facts are true and will help extend the life of your tires. After all, race cars, commercial airliners and over-the-road trucks have been using it for years. But, will Nitrogen keep you from getting a flat or help prevent sliding, spinning or skidding? Not likely. By keeping the tire pressure more consistent, it can be argued that ride, handling and fuel economy may be improved, but whether you will actually feel a difference or not is debatable.
Most facilities that offer Nitrogen tire service have equipment that manufactures the gas on site and install it – I have not seen any Nitrogen conversion kits for sale at local auto parts stores. The cost of the service varies, and depending on the age and condition of your tires, may not be cost effective. I've seen pricing from $2 to $10 per tire.
The best time to go Nitro would be when replacing tires or buying a new vehicle. With many new vehicles now featuring tire pressure monitoring systems (TPM), using Nitrogen could reduce false error messages or warning lights coming on by keeping tire pressure more consistent. Tire pressures will still vary some when taking a long trip, but you want to make sure that all four tires have either Nitrogen or CO2 to keep from confusing the system. Since you can’t see what’s in your tires, be sure to use a reputable tire store or service provider or else cool green valve caps may be all you get for your money.
For more information see http://getnitrogen.org/