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Did you know you're already inflating your tires with nitrogen? Well, mostly. You're also inflating your lungs with mostly nitrogen, as the same air we breathe and use in our tires is comprised of 78% nitrogen, 21% oxygen, and 1% other gases. So what's all this talk about using pure nitrogen in our tires? Let's take a look at the pros and cons.

Pros of Nitrogen Filled Tires

Proponents of nitrogen claim that it improves gas mileage in two ways. First, nitrogen is not susceptible to pressure changes because it is free of moisture. Regular air can retain moisture which leads to the air contracting and expanding more significantly under varying temperatures. In cold conditions, the moist oxygen will shrink, leading to a reduction in tire pressure. This reduction in pressure causes a decrease in gas mileage because there's more tire on the road to create friction. More friction means the engine must work harder to propel the vehicle forward. Conversely, in extremely hot temperatures, regular air in tires can expand to a potentially unsafe pressure level.

Nitrogen molecules are also less likely to seep through the tire's rubber walls; therefore the tires retain their optimal pressure for a longer period of time. Again, a properly inflated tire should lead to better gas mileage compared to an under-inflated tire. Racing teams have been filling tires with nitrogen for years, as they are looking to squeeze every extra drop of performance out of the car that they can.

Another well publicized reason for using nitrogen is safety. Modern day aircraft tires are inflated with nitrogen, because it is a non-combustible gas. Aircraft tires that are under a high amount of pressure can overheat and explode, creating a fire hazard if inflated with air containing combustible oxygen.

Cons of Nitrogen Filled Tires

The primary con here is the extra cost of using nitrogen. Expect to spend around $10 more per tire if you plan to use nitrogen, not to mention the hassle of finding a nitrogen vendor and the incremental cost of replacement valve stem caps.

There has yet to be a valid study that proves the claims that nitrogen improves fuel efficiency. The theory looks good on paper, but in practice, the results are inconclusive. Nitrogen advocates point to anecdotal evidence of increased mileage but have yet to prove it scientifically in the real world.

Eventually you'll need to find more nitrogen, as the tires will gradually lose pressure even with 100% nitrogen. If you need to replace a tire due to a blowout, or if you purchase new tires, you'll have to get your wallet out again. At this time, there aren't any fuel stations offering pure nitrogen fill-up services.

Final Thoughts

It's unlikely you'll be driving at race car speeds or exerting the level of pressure on your tires that aircraft do, so the safety concern should not be a factor. You can spend a little extra per tire to gain the perception of increased gas mileage and less frequent tire refilling. Unfortunately, it's only a perception. The best option for now is to ensure your tires retain their optimal pressure year-round and save the extra cost and hassle.

Learn more about this author, Ken Reigle.
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