Should I put nitrogen in my car’s tires?

Have you ever noticed that some vehicles have a green valve cap on the tires? Is that some sort of special aftermarket modification? In general, the green caps indicate that the vehicle’s tires are filled with nitrogen instead of air.
Wait a second, doesn’t the bulk of atmospheric air consist of nitrogen? Yes.
78%

Percentage of nitrogen in normal air-filled tires.

95%

Percentage of nitrogen in nitrogen-filled tires

The last time I was shopping for a car at the dealer, the salesman was heralding nitrogen in the vehicle’s tires as a godsend. This godsend also came with a hefty price tag of $700! What advantages does increased nitrogen in the vehicles confer?

We all [hopefully] have been instructed to make sure our car’s tires are properly inflated. The proper tire pressure for your vehicle is usually indicated inside the driver side door.

Sometimes the numbers are identical for all four tires, but not always the case. My Subaru recommends maintain a pressure of 33psi in the front tires and 30psi in the rear tires. Keeping the the tires properly inflates confers two advantages:

  • Symmetrical wear on tires: Obviously if the tires are overinflated or under inflated for long periods of time, there will be uneven wear on the tires. This is most certainly reduce the longevity of your tires and can result in misalignment with drifting of the car when driving straight.
  • Optimal fuel economy: I remember reading an EPA study showing that there is a 0.3% decrease in fuel economy per 1psi decrease in a tire’s pressure. You can easy have a drop of 25% in tire pressure over a year’s time if you don’t check frequently. For most vehicles, you might lose 1-2 mpg depending on your driving habits.

 

 

Nitrogen supposedly is able to remain in the tire more readily than room air because the molecule is larger. If nitrogen is less apt to escape, then the tire will maintain better wear and fuel economy. Does this work in practice? I certainly have not noticed a difference in the brief period that I’ve had nitrogen.

The third benefit of nitrogen in your tires is decreased wheel corrosion. Oxygen, as we know, is a key component in oxidation. After 8 years in the tough northeastern snowstorms, my alloy wheels became quite corroded and had constant rim leaks no matter how much I scrubbed the rims and put bead sealer to keep the air in. In practice, having oxygen in my tires may have helped delayed the corrosion, but with the amount of winter snow, road salt, and ice I went through, I’m not sure if it would have helped.

What situations will nitrogen help in tires?

I’d imagine that mission critical and high performance situations will require stable tire pressure the most. That would probably be for race cars, airplanes, and spaceships. These vehicles undergo significant temperature changes during operation.

Should I put nitrogen in my car’s tires?

If you’re read this far, you probably realize that I’m not too convinced about the benefits of nitrogen in tires, especially if you have to pay some $700 extra for a vehicle. That being, said, I actually have nitrogen in my car’s tires. It came free when I purchased new tires at Costco. You can always have the tire guys there check the pressure at any time.

Do you use nitrogen in your car’s tires?

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