Should You Use Nitrogen in Your Car Tires?
CR's tests show that using nitrogen is not worth the money or inconvenience
This common pitch is compelling: Filling your car’s tires with nitrogen will reduce air loss, boost fuel economy, reduce rolling resistance, and improve safety. Some cars are even sold with the telltale green caps on valve stems, signaling the tires have already been filled with nitrogen.
Dealerships and tire shops often charge owners to fill tires with nitrogen, at $5 or more per tire, during routine service visits or when replacing tires. But is nitrogen worth the price?
How We Tested Air Loss
Consumer Reports conducted a 12-month study at our Auto Test Center using 31 tire models of all-season tires. The tires and wheels were purchased new, and they were used for our 16,000-mile treadwear test.
We first ensured that we had 95 percent nitrogen purity in the tire—the claimed limit of our nitrogen system, which generates nitrogen gas from ambient air and removes water vapor.
We filled one tire per model with air and another with nitrogen. Both were filled to 30 psi (pounds per square inch) at room temperature. We set both tires outdoors for one year, then checked the inflation pressure at room temperature again.
Both tires lost pressure over that time, but the difference in loss was minimal. The average loss of air-filled tires was just 3.5 psi from the initial 30 psi setting. Nitrogen-filled tires lost an average of 2.2 psi.
The results show that nitrogen does reduce pressure loss, but the reduction was only a 1.3 psi difference from air-filled tires over an entire year.
“Our test showed that while nitrogen has some advantages, both nitrogen and air-filled tires lose pressure over time,” Pszczolkowski says. “It is important that car owners routinely check their tire pressure.”
We have concerns that car owners who use nitrogen might check their tire pressures less often. That would be a mistake, Pszczolkowski says.
What NHTSA Found
The NHTSA study also found that regular air escapes tires at a higher rate than pure nitrogen does.
The government agency concluded that using nitrogen does reduce tire degradation by limiting oxidation. Oxidation refers to the damage caused by exposing tires to the oxygen in regular air, which can make rubber become brittle. However, this is not a practical concern for most consumers, because they replace the tires long before degradation is a problem.