“Should I believe the hype about putting nitrogen in my tires?”

This question is answered best with an internal memo from the engineers of Honda:

Surf any automobile tire-related website these days, and you’ll likely see something mentioned about nitrogen inflation. It’s becoming a hot topic. We’ve gotten a number of inquiries lately concerning American Honda’s position on this practice. When it comes to inflating automobile tires, it’s our position that ordinary, dry-compressed air — which is about 80% nitrogen already — is the best choice. That’s because it’s more readily available, and the benefits of using nitrogen simply don’t appear to outweigh those of using compressed air. The practice of inflating tires with nitrogen really isn’t anything new; it’s been around a long time. It’s been commonly used on aerospace vehicles, commercial and military aircraft, military vehicles, race cars, and even heavy off-road construction equipment. Here’s why:

To meet rigid safety and performance specs, the required tire inflation pressures are often very high, especially in the aerospace industry. The tire inflation pressure for NASA’s space shuttle, for instance, is a whopping 315 psi!
Nitrogen is an inert gas; it doesn’t combust or oxidize.
The process used to compress nitrogen excludes water vapor. Water vapor can expand if the temperature climbs above 212 degrees Farenheit

Tires inflated with nitrogen leak more slowly over time than those inflated with compressed air. Automobile tires, on the other hand, are subjected to an entirely different set of conditions. Here’s why inflating tires with nitrogen offers no real advantages:

Although tires inflated with nitrogen leak slower over time than those inflated with compressed air, they still leak and need to be reinflated periodically to maintain pressure. If you can’t find a place that offers nitrogen inflation — and there aren’t yet all that many places that do — your only option left is to reinflate with compressed air. Doing that drops the nitrogen purity.
Nitrogen offers no better protection against road hazards such as cuts and punctures. So no matter what you inflate the tire with, you still need to check the condition and pressure of the tires at least once a month as recommended in the owner’s manual.
Tires that are inflated with compressed air and properly maintained offer the same fuel economy, tread wear, and ride comfort as those inflated with nitrogen.

Nitrogen for automobile tires is produced by nitrogen generators, which typically get about 95% purity. But to actually get that level of purity into an automobile tire, you would have to deflate and inflate that tire with nitrogen several times. If you’re not careful doing this repeated deflation and inflation process, the purity level winds up being closer to 90%. When compared with normal compressed air, which is about 80% nitrogen to begin with, you may start to wonder if there is any benefit at all. Because of this, those claims of less pressure loss with nitrogen aren’t valid.

So here’s the bottom line: Nitrogen is an ideal gas for inflating tires in aircraft, military vehicles, race cars, and heavy off-road equipment, but when it comes to automobile tires, it offers no apparent advantages over ordinary, dry-compressed air. Our advice to you: Just stick with the air you breathe!