Nitrogen-filled tires: Better Mileage & Safer Driving?

When you drive over the mountains and through the woods to grandmother's house next week, you should check the pressure in your tires to make sure your drive is safe. More local stores are now putting nitrogen in tires instead of compressed air. They say it can help your car get better mileage and drive safer. Nitrogen may cost you $2 to $20 per tire. Is it worth it? We look into it in this Seven On Your Side Consumer Watch.

When rubber meets the road on the Nascar track, the tires are often filled with nitrogen instead of air.

Stores like Costco are filling tires with nitrogen, too. The Get Nitrogen Institute says a tire filled with nitrogen maintains its pressure three to four times longer than compressed air. Proper tire pressure helps your car get better gas mileage and drive safer. Said Daniel Griffiths with Costco, "When you maintain a more constant pressure, you'll have a more constant contact patch, which is a part of the tire that contacts the road."

Proponents say nitrogen molecules are larger than oxygen molecules, so it's harder for them to escape the tire. They also say nitrogen resists heat build up and moisture that can damage the inside of your tire. Explains Griffiths, "Nitrogen is dry so you won't have any moisture in your tire."

We measured the pressure in a tire on a car filled with nitrogen after a month of driving. The pressure measured about 35 pounds, about the same as the pressure originally put into the tire.

Consumer Reports says it conducted a test of tires sitting outside for a year. Those with nitrogen lost only about one point three pounds less than tires with compressed air. Said David Champion with Consumer Reports, "From the testing that we've done, we've seen that it doesn't do any harm but it's probably not worth paying for."

The Get Nitrogen Institute refutes the study, writing in a letter to Consumer Reports it shared with us, "The study did not take normal driving conditions into account, thus bypassing an extremely important set of variables ...."

The Get Nitrogen Institute tells us Clemson University conducted a study showing tires filled with nitrogen on passenger cars saved 6% more fuel and lost 35% to 55% less air pressure.

Whether you use nitrogen or air, you still have to check the pressure in your tires. Said Griffiths, "They should always check it at least once a week, at minimum once a month."

So where can you get your tires filled with nitrogen? Here's a link to www.getnitrogen.org  where you can type in your zipcode and it will list Upstate stores that offer nitrogen for tires.