You Don't Need to Fill Your Car's Tires With Nitrogen

Getting a new set of tires for your car isn't cheap, so it's hardly surprising that people want to protect their investment and do what they can to extend their lifespan. Some attempt to do this by filling their tires with nitrogen, instead of the traditional compressed air found at gas stations.

While nitrogen reportedly has some advantages, it also comes with a higher price tag than gas station air. So, is it worth it? After one year of testing, the automotive experts at Consumer Reports concluded that it's not. Here's what to know.

What's the difference between putting nitrogen versus regular air in your tires?

Traditional compressed air used to fill tires is made up of 78% nitrogen and almost 21% oxygen, with the remaining percentage consisting of water vapor, carbon dioxide, and small concentrations of noble gases, like neon and argon.

Though many gas stations and rest stops offer compressed air for free, others charge between $1-2 for enough air to top off all four tires. Nitrogen, meanwhile, costs $5 or more per tire, and typically is only available at tire shops and dealerships.

What are the benefits of filling tires with nitrogen?

It's becoming increasingly common for the tires on new cars to come filled with nitrogen--those were have green caps on the valve stems. When dealerships do this, it's often accompanied by a pitch on the benefits of nitrogen in an attempt to convince customers to return for a refill. Oft-touted advantages of nitrogen include improved safety, reduced air loss, better fuel economy, and reduced rolling resistance, per Consumer Reports.

Is filling your tires with nitrogen worth it?

In short: No. After 12 months of extensive testing, the team at Consumer Reports found that "the benefits are more theoretical than practical."

When it comes down to it, most of the supposed advantages of filling your tires with nitrogen have to do with maintaining proper tire pressure, says Ryan Pszczolkowski, Consumer Reports' tire program manager.

To determine the validity of those claims, the team at Consumer Reports tested 31 different models of all-season tires in pairs--filling one tire with nitrogen and the other with regular compressed air, each to 30 psi (pounds per square inch) at room temperature. They left the tires outdoors for a year, then checked the inflation pressure at room temperature again.

After 12 months, the tires filled with compressed air lost an average of 3.5 psi (out of 30 psi), while those filled with nitrogen were down an average of 2.2 psi.

The bottom line

Technically, the nitrogen-filled tires did hold onto slightly more air pressure, but the difference was so minimal that the team at Consumer Reports determined that nitrogen wasn't worth the additional cost and hassle.

Plus, some experts worry that people may use the supposed advantages of nitrogen-filled tires as an excuse to neglect regular maintenance.

"It is important that car owners routinely check their tire pressure," Pszczolkowski says. "We have concerns that car owners who use nitrogen might check their tire pressure less often. That would be a mistake."