Should You Use Nitrogen in Your Car Tires?

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 pressure less often. That would be a mistake, Pszczolkowski says.

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.

As anyone who has had a flat tire can explain, tires don’t hold up a car by themselves: They need to be filled with air. Pressure changes over time, with temperatures affecting the air density and the air permeating the rubber. Check tire pressure once a month, when the tires are cool in the morning, and top off as necessary with regular air. It’s a low-cost way to bolster your car’s safety and fuel efficiency.

“Routine maintenance is critical to long tire life and good health. Proper tire inflation pressure is the objective,” says Woody Rogers, vice president at Tire Rack, a major national tire retailer. “Air works fine and is essentially free.”

There is a stronger case to be made for nitrogen for high-tire-pressure, heavy-duty applications, ranging from large commercial trucks to airplanes. But based on our experience with passenger cars and these test results, consumers would be better served—and would save their money—by just using air in their tires and checking them monthly.

There is nothing wrong with using nitrogen in passenger cars and trucks, but it does take commitment and potentially cost. Nitrogen users should be diligent about topping off only with nitrogen to ensure they are getting the intended benefits.