Fill Your Car’s Tires With Nitrogen

The Get Nitrogen Institute Web site says that with nitrogen tire inflation, drivers will note improvements in a vehicle’s handling, fuel efficiency and tire life. This sounds great in theory but let’s take a closer look at each of those claims.

  • Better tire-pressure retention: Over time, a tire will gradually lose pressure. Changes in temperature will accelerate this. The general rule of thumb is a loss of 1 psi for every 10-degree rise or fall in temperature. The institute says that nitrogen has a more stable pressure, since it has larger molecules than oxygen that are less likely to seep through the permeable tire walls.
  • Improved fuel economy: The EPA says that under-inflated tires can lower gas mileage by 0.3 percent for every 1 psi drop in pressure of all four tires. The theory is that since nitrogen loses pressure at a slower rate than air, you are more likely to be at the correct psi and therefore get better fuel economy. If you are proactive and check your tire pressure at least once a month, you can offset this difference with free air, and you won’t need expensive nitrogen. We think this invalidates the “better fuel economy with nitrogen” argument.
  • Cooler running temperatures: When air is pressurized, the humidity in it condenses to a liquid and collects in the air storage tank you use at the local gas station. When you add compressed air to the tire, the water comes along for the ride. As the tire heats up during driving, that water changes to a gas, which then expands, increasing tire pressure. Because nitrogen is dry, there is no water in the tire to contribute to pressure fluctuations.
  • Prevent wheel rot: Nitrogen proponents will also point out that water in a tire can lead to wheel rot. A tire engineer who anonymously maintains Barry’s Tire Tech, a blog on a number of tire issues, says this isn’t really a problem with modern cars.

Cost and Convenience 
Let’s say a person bought a set of tires at Costco, a place that uses nitrogen to fill all the tires they sell. If he needs to top off the tires with more nitrogen, he won’t be able to go to just any gas station. He can use regular air if there is nothing else available, but that would dilute the nitrogen in the tires. He’ll have to go back to Costco and wait until the tire technicians can attend to the car. On a busy day, he could be there awhile.

Is Nitrogen Worth It? 
The air we breathe is made up of 78 percent nitrogen, 21 percent oxygen and a few other elements. To get the desired benefits for tires, nitrogen needs to be at least 93 percent pure, according to nitrogen service equipment providers quoted on Tirerack.com. So we’re basically talking about adding an extra 15 percent of nitrogen and getting rid of as much oxygen as possible. Based on cost, convenience and actual performance benefit, we don’t think nitrogen is worth it. A much better use of your money would be to buy a good tire-pressure gauge and check your tires frequently. This is a good idea even if you have a tire-pressure monitoring system in your vehicle. The warning lights aren’t required to come on until you have less than 25 percent of the recommended tire pressure. Having the correct tire pressure will get you many of the benefits of using nitrogen and will ensure that your tires last longer.