If you’re not particularly into science, don’t worry. We won’t bog you down with anything too technical here. But when discussing the differences between filling tires with nitrogen versus oxygen, one does have to discuss molecule composition. There’s a difference between nitrogen and oxygen molecules that can have an effect on your tires and you can read about those differences below.

Tire Pressure Stability
When compared to the compressed air from your local gas station (which is composed of oxygen and a small percent of water vapor), nitrogen is composed of larger molecules. What does this mean for your tires? Imagine for a moment that you can see your tire significantly magnified. If you could look way up close you’d see very tiny openings in the rubber. Nitrogen molecules, which are larger in size, will have a harder time leaking out of the tire walls, while the smaller oxygen molecules in compressed air leak out more easily.

This leads to a simple fact: Nitrogen filled tires retain more even tire pressure because they’re less prone to leak air, meaning less issues with low tire pressure.

Moisture Isn’t Friends with Nitrogen
Because nitrogen is a dry gas, you won’t experience the tire overinflation that can occur with compressed air. Like we mentioned above, the compressed air at your local gas station includes a bit of water vapor. When it’s hot out, the water vapor can turn to gas and expand the tire. Overinflation can be dangerous when driving on hot Arizona roads, so if you use compressed air (or even nitrogen) make sure you check your tire pressure regularly.

Nitrogen Optimizes Fuel Efficiency
Underinflated tires cause a slight decrease in fuel economy because the car then has to run harder to accelerate. As noted above, nitrogen molecules are resistant to leaking out of tires, which means underinflation (i.e., low tire pressure) is much less likely. A notable benefit of filling tires with oxygen is that you can ensure your car achieves maximum fuel economy more often than when using compressed air, since nitrogen filled tires aren’t prone to underinflate.