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Tire Inflation : Air or Nitrogen : What Should You Use?

There’s been an ongoing debate about tire inflation.  Most drivers scratch their heads when they hear that. Surely air goes into tires, right? There’s an alternative available, pure nitrogen. Air or nitrogen – what should you use?

Which is the right choice for your car? The short answer is that for most drivers, air works just fine. For performance vehicles and specific situations, nitrogen offers several advantages.

To help you choose, here is a look at the difference between nitrogen and air in your tires.

Tire Inflation - Air or NitrogenIt Starts with Tire Pressure

To keep your tires functioning at peak levels, you need to regularly monitor inflation pressure. When the pressure goes down, your tires experience greater rolling resistance, which affects your gas mileage.

According to the Environmental Protection Agency, your gas mileage drops about 0.3 percent when your tire pressure goes down 1 pound per square inch, or psi. This is true whether you use air or nitrogen in your tires.

Air and nitrogen, like all gases, swell up in heat and shrink in cold. For every 10 degree Fahrenheit change in the temperature, you can expect your tires to go up or down 1 psi.

That’s why the best time to check your tires is early in the day, before heat from driving or the sun causes pressure to rise. This gives you the most accurate reading.

And you need to check regularly, at least once a month and before you head out on a long trip. In some areas, road conditions and even local regulations dictate checking twice a month. That includes the spare tire, which often gets forgotten.

Every tire and car is different, so find out what the manufacturer recommends. This information is in your owner’s manual and on the tire placard on your car or truck.

Basic Differences Between Air and Nitrogen

The normal air you put in your tires has a significant amount of nitrogen already, about 78 percent. In addition to nitrogen, dry air consists of just 21 percent oxygen, and the rest is made up of CO2, water vapor, some neon, argon and small amounts of other gases.

Nitrogen in tires is typically 93 to 95 percent pure. Fundamentally it is just air with all the oxygen taken out. This makes it non-flammable and not subject to problems caused by moisture. This makes nitrogen the best choice for aircraft, heavy equipment, in mining and auto racing.

But that doesn’t mean it’s the most sensible choice for the average driver.

Air or Nitrogen : What Should You Use?

Here is a closer look at the pros and cons of nitrogen and air.

Air

Air offers two major benefits for the average driver: the cost is low and it is easy to find.

  • Free or low-cost. Cost-conscious drivers opt for air. It is often available free or for a nominal charge.

  • Many locations. Most gas stations have air available so you can add it quickly when you fill up your gas tank. Or your tire dealer will often do the work for you, checking the pressure and filling up the tires as needed. This is also part of the service in most places when you get your oil changed.

Nitrogen

Nitrogen has three major advantages over air, though neither has a significant effect on the average driver.

  • No oxidation. Nitrogen can slow the effects of age on your tire, and reduce corrosion to the wheel. Nitrogen is a dry gas and doesn’t support the buildup of moisture. . When a driver puts 93 to 95 percent nitrogen in his tires, the negative impact of oxidation is no longer a worry. How important is that to the average driver?On a practical level and in regard to the tire itself, it isn’t. Tire experts point out that you’ll need to worry about the tread on your tires long before you need to be concerned about oxidation. So you’ll be buying new tires because of tread before you see the aging effects of moisture on wheels and tires.  HOWEVER, in regard to sensitive equipment inside the tire, this can be important…

  • TPMS Sensors and Other In-Wheel Electronics. I was in the tire shop last month having new wheels put on my vehicle.  While waiting, I overheard the service tech explaining to a customer just what we’re talking about here – Nitrogen vs. air in the tires.  And like a sign from above, another customer came in holding a corroded TPMS sensor (the gadget inside each wheel that sends low pressure signals to your vehicle’s onboard computer).  TPMS stands for “Tire Pressure Monitoring System”.  This guy’s sensor was destroyed by the corrosion caused by using air in the tires.  The service tech showed the other customer and said “THIS is exactly what I’m talking about.”  Knowing that I just purchased four new TMPS sensors from my local Toyota dealer at $130 EACH, and was paying to have them installed, I right then decided I’d go the Nitrogen route.  Note that depending upon the vehicle, TPMS sensors can range from $30 each all the way upwards of $350 EACH.  The extra $20 for nitrogen was cheap insurance in my opinion.
    Nitrogen and TPMS Sensors

    A TPMS Sensor installed on a wheel. Image courtesy of CarID.com


  • Steady air pressure. Nitrogen does keep your tire pressure steady for a longer period than air does. That’s because nitrogen has bigger molecules than air, so it passes through the tire at a slower rate. But according to Consumer Reports, the tiny improvement was minimal. You still need to check the tire pressure regularly. The group studied 31 pairs of tires over 12 months, one with air, one with nitrogen. The loss was 3.5 psi for the tires with air, and 2.2 psi for the nitrogen tire.

  • Special situations. If you have a race car, operate an airplane, or use heavy equipment in your business, your vehicle will operate better with nitrogen. Under extreme conditions, nitrogen gives you more control over the pressure in your tires. That can be critical for safety and performance, in special situations that the average driver never faces.

Nitrogen also has two major drawbacks, cost and ease of use.

  • Higher cost. To fill your tires with nitrogen costs $5 to $7 dollars for each tire, compared to free or $1 to $2 for air. To first upgrade from air to nitrogen, you need to spend $70 to $180 at a tire shop. That’s because the tires must be filled and then deflated numerous times to get all the air out. Unless you have 93 to 95 percent pure nitrogen in your tires, you won’t get any benefit.

  • Trouble finding it. In most cases, you need to go to a tire dealer to add nitrogen to your tires. Very few gas stations offer it. And not all tires dealers do.  Some tire shops though offer nitrogen free for the lifetime of the tire.  For example, if you’re on the road and need to put air in the tire you can later go back to the tire shop and they will empty the tire and refill with pure nitrogen (ask first though).

Both

One area where air and nitrogen are evenly matched is mileage. According to a study done in 2008 by ExxonMobil, nitrogen doesn’t affect the rolling resistance of your tires. And that’s what determines fuel economy. Whichever you use, you’ll probably get the same mileage.

Should you make the switch? Nitrogen has certain performance advantages over air, though it’s harder to find and more expensive. For most drivers, it’s not necessary.

 

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