Lately, I have been receiving questions in the forums, as well as on the phone about running pure nitrogen in tires. Unfortunately, there are many shops out there that are overstating (and overcharging) for this service. Below are some common facts and myths to consider before filling your tires with nitrogen.
Fact: Air that we breath and put into our tires is roughly 78% nitrogen.
This is correct. Tires are typically inflated with air that's a combination of approximately 78% nitrogen, 21% oxygen and 1% miscellaneous gases.
Myth: Using pure nitrogen in tires will increase fuel economy.
A tire's fuel economy is not affected by the type of air inside the tire. Lower air pressures can lead to lower fuel economy and nitrogen is a gas that is still affected by changes in ambient temperatures (about one psi for every 10ºF Fahrenheit). Using the correct inflation pressure not only provides the appropriate load capacity, it also contributes to the vehicle's fuel economy.
Fact: Pure nitrogen-filled tires will lose slightly less air over time.
It is true that nitrogen does not escape a tire's airtight seal quite as easily as oxygen (most air-filled tires will lose about 1/2 to 1 psi per month), so a pure nitrogen-filled tire should lose less air pressure over time. Nitrogen reduces the lost of tire pressure due to permeation through rubber over time by approximately one-third. This does help maintain the vehicle's tire pressure a little longer, but does not eliminate the need for monthly checks of tire pressure.
Myth: Pure nitrogen-filled tires will run cooler.
This is another myth that is tied to the assumption that consumers will not check their air pressures often enough. Simply having a different type of gas in your tires will not make them run cooler.
Myth: Nitrogen-filled tires last longer.
The type of air inside a properly inflated tire does not affect the tire's tread life. While there is evidence to suggest that nitrogen-filled tires will have less oxidation to the inner liner of the tire, keep in mind that a tire's inner liner was specifically designed to handle standard air. There is no proof of any tire failing due to rubber oxidation caused from the tires having standard air inside them.
The only benefit from running pure nitrogen in tires is the increased air retention (slower loss of air out of the tires over time). A tire that is normally maintained with the proper air pressure will perform exactly like a tire with a pure nitrogen fill. If you can get a pure nitrogen fill for free, there is no harm in doing so but very little (if any) benefit from it.
For more information on nitrogen tire inflation, read "Clearing the Air About Nitrogen Tire Inflation."