Busting The Nitrogen Saves Gas Myth

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 a basic principle. Inhale...., now let it out. The breath you just took was 78% nitrogen. Of course you could tell that when you took that breath, couldn't you. That is the biggest problem with the assertion that nitrogen is better than air. 78% of the air is already nitrogen!

A major claim made by nitrogen advocates is that nitrogen is a larger molecule and will permeate through the tire slower than oxygen. By slowing the seepage out of the tire, nitrogen will allow you to maintain the proper pressure in the tire longer.

The natural laws of physics don't support that contention. The rate of seepage of a gas through a porous membrane depends on it's mass and on it's size. Nitrogen and oxygen are almost the same size and nitrogen is slightly lighter than oxygen. If either gas is going to seep through the tire then the nitrogen would actually seep slightly faster than the oxygen.

Applying some common logic to this can illustrate why the nitrogen supposition is false. If oxygen did escape through a tire at higher rates than nitrogen, then as the oxygen escaped, the tire would be left with mostly nitrogen. Assuming this is what happens, then over time as oxygen has been lost there might be 91% nitrogen on the residual air in the tire instead of the original 78%.

Now in order to bring your tire back to the proper pressure, you top off your tires with a small amount of air. You have in effect added a small amount of air which is 78% nitrogen to the residual air in the tire which is 91% nitrogen. The end result is your tire is now filled with an air mixture with a very high 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.

If this were the case, that the oxygen leaves the tire while the nitrogen is left behind, you would eventually end up with nitrogen filled tires. All the while just filling them with air. Since you now have nitrogen filled tires why on earth would you fill your tires with nitrogen to begin with and spend the extra money?

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.

As is generally the case there are those who always take advantage of some problem to make a profit. Who gets the benefit of filling your tires with nitrogen? Non other than the manufacturers of the nitrogen producing equipment and the merchants who sell the nitrogen to the public. They make more money. Who ends up paying for those extra profits? That' right, it's you.