For the first time in history, there's a new trend in tire filling. Normally, tires are filled with regular old compressed air. In recent years, however, a new development has arrived on the scene: filling tires with nitrogen.

Some tire dealers now offer this service to their customers, but is it really worth it? After all, filling your tires with compressed air has a maximum charge of about 25 cents four all four tires, and that money usually goes to charity. Many service stations still offer the use of their compressor for free.

Filling your tires with nitrogen, on the other hand, does have a definite cost. You can expect to pay anywhere from two to ten dollars per tire. This is not too high a price to pay, if nitrogen filling can really deliver all that it claims.

According to the companies that manufacture nitrogen compression systems, nitrogen filling will help to save money on not only tire replacement, but gas as well. This is because a tire, over time, will lose miniscule amounts of compressed air through microscopic holes in the tire surface. This will lead to pressure loss. Although you may not notice a change in the vehicle's handling with a drop of 1-2 psi, it can seriously affect mileage. As the tire loses pressure, more of its surface comes into contact with the road. This increases friction, meaning the engine works harder. It can even lead to a blowout.

Also, oxygen, which is obviously present in large amounts in compressed air, is a terribly reactive element. Think of rust, rot, and decay and you have a pretty good picture of what oxygen can do.

Pure nitrogen, however, doesn't have these problems. Unlike oxygen, nitrogen doesn't react with the rubber found in tires, so new tires filled with nitrogen will definitely last longer than ones filled compressed air. Because of this, those microscopic holes will not develop, meaning that a tire filled with nitrogen will stay at optimum pressure for longer, barring actual punctures or leaks in other areas.

It is worth noting that race cars, military vehicles, and many types of aircraft (including the Space Shuttle) use nitrogen in their tires. Should you?

The question is really one of economics. The above mentioned vehicles use nitrogen instead of compressed air primarily because those tires are extremely expensive (especially on the Shuttle. When you're total market for a specially designed tire consists of less than ten vehicles you have to charge a lot just to break even).

If your tires are old and due for replacement, then spending money filling them nitrogen is probably a fool's errand. However, if you have recently made an investment in high-quality premium tires, then a further investment in nitrogen filling is the way to go. Although the savings in gas may be small, they definitely do exist, and in today's marketplace every little bit helps. More importantly, your tires will last considerably longer.