The Truth About Nitrogen and Saving Gas

Nitrogen as an alternative to air when filling tires seems to be gaining some popularity. The fact that Costco and other retailers are now offering nitrogen fills certainly points to nitrogen filled tires as becoming more mainstream. At almost $10 per tire does it really save fuel like it is claimed to do? Here are some answers.

Let's start with the most basic principle of all. Take a deep breath. Now let it out. You realize that the breath you took was 78% nitrogen. I'll bet you couldn't tell. Therein lies the biggest problem with the theory that nitrogen is better than air. Air is already 78% nitrogen!

The basic claim made by nitrogen supporters is that nitrogen will permeate through the tire slower than oxygen because it is a larger molecule. By slowing the pressure loss of the tire, nitrogen will allow your tires to maintain the proper pressure longer.

This contention is just not supported by the laws of physics. The rate of diffusion of a gas through a porous substance depends on the mass and the size of the molecules of that gas. Oxygen and nitrogen are almost the same size and in fact nitrogen is lighter than oxygen. That means that if either is going to permeate through the tire the nitrogen would actually permeate faster than the oxygen.

Think about this for a minute. If oxygen actually permeated out of a tire faster than nitrogen, then as the tire deflated what would be left in the tire would be mostly nitrogen. Let's say there was 90% nitrogen left in the tire.

You then go to the station and top off your tires which are now filled with a high concentration of nitrogen. You add a small amount of air to the tire. Now you have much less oxygen in the tire than you did when you first inflated it. It has a much higher concentration of nitrogen.

Continuing this train of thought, if the nitrogen does continue to behave the same way, the smaller amount of oxygen now in the tire escapes from the tire and the nitrogen that remains behind becomes even more concentrated. Maybe you now have 95% nitrogen in your tires. As you continually repeat this process many times, you continue to get higher and higher concentrations of nitrogen in your tires. Eventually you will end up with only nitrogen.

The question is, if eventually you would end up with nitrogen filled tires by just repeatedly filling them with air, why would you fill them with nitrogen to begin with and spend the more money? It just doesn't make sense.

This is just a plain logical example as to how false the nitrogen claims are. There of course are a myriad of specific scientific answers showing why the nitrogen claims are based on myths and not scientific facts. Each one would require a separate article in itself to explain. In the end it seems you are seeing the single law of behavior that seems to play itself over and over.

Once again there are those who are taking advantage of a situation to make a buck. Who finds an advantage to filling tires up with nitrogen? Those selling the equipment and those retailing the nitrogen. They earn more profits. Who gets the short end of the stick? That' right, it's the consumer.