A popular idea, using nitrogen in order to save gas seems to be gaining supporters. It is used as a substitute for air when filling tires . Even retailers like Costco are now offering nitrogen fills. The cost of nitrogen is about $10 per tire. Is nitrogen worth the additional dollars? The answer is no!

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 big claim made by nitrogen believers is that nitrogen will save gas by keeping your tires at the optimum pressure level. They suggest that nitrogen permeates from your tires slower than oxygen. The pressure loss of the tire is less over time because the nitrogen is staying in the tire 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.

Consider this little bit of common logic. If oxygen did indeed permeate through a tire at a faster rate than nitrogen, then as the tire lost pressure mostly nitrogen would then be left in the tire. Let's assume at this point there is 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.

Assuming that the oxygen continues to leave the tire and the nitrogen remains you would have an even higher percentage of nitrogen in your tires. Maybe 95%. As you repeated this over and over you would eventually have nothing but nitrogen in your tire.

Based on the claim that oxygen would leave the tire faster, you would end up with nitrogen filled tires while filling them with air. If this were the case then what would be the point of filling your tires with nitrogen to begin with?

This is just a common sense answer as to why the claims of nitrogen being a significant factor in reducing gas consumption just don't hold up. There many more specific scientific answers as to why the nitrogen claims are false. Most of them are way to complicated to try and explain in one short article. In the end it seems you are seeing the one law of physics that seems to manifest 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.