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!
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.
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.
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 your tires off with air to bring them back to the proper pressure. Now you have almost all nitrogen in the tire that you added a small amount of air to. At that point you would have much less oxygen in the tire than you did when you first inflated it.
Continuing this scenario, as it is claimed, the oxygen continues to dissipate from the tire and the nitrogen remains behind. Now you have an even higher amount of nitrogen in your tire. Maybe 95%. As you repeat this process again and again your tire would eventually end up being full of only nitrogen.
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.
Scott Siegel is the author of a 143 page book of industry insider secrets on saving gas and dollars at the pump (beatthegaspump.com). Visit us to learn how you can get better gas mileage. Find out how to increase gas mileage.
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