Over the past couple of years, you may have noticed that many tire and repair shops have been offering nitrogen-fills for tires, rather than simple compressed air. Perhaps a service manager made a persuasive case as to why you should convert your tires over from plain old compressed air. Let’s look at the nuts and bolts of this concept.

Claims
– The nitrogen molecule is larger than an oxygen molecule, so nitrogen is less prone to permeate the pores of the tires. Hence, the tire maintains a more constant inflation pressure. This leads nitrogen installers to claim that this concept will lower rolling resistance, save fuel, improve tire wear and safety.

– Moisture can be present in oxygen filled tires, whereas nitrogen offers dry environment inside the tire. Overtime, the presence of moisture can contribute to tire oxidation and/or rim corrosion. Both issues can lead to slow leaks.

So is it worth it?
Isn’t that old-fashioned compressed air comprised of 78 percent nitrogen (and 21 per cent oxygen) anyway? Yes it is, but let’s look deeper.

The cost of filling each tire with nitrogen is somewhere between $5 and $7. Yes top-ups are free, but that is only if you are in need of a fill near the shop or outlet of the chain that did the initial installation.

There are no known studies to suggest that nitrogen alone will lower the rolling resistance of a tire. This is an extension of the claim that nitrogen will maintain a more constant inflation pressure. Checking your oxygen-filled tire pressures on a monthly basis will accomplish the same goal.

This applies also to the suggestion that nitrogen will save fuel, improve tire wear and safety. Again, a properly maintained oxygen-filled tire will roll down the road in exactly the same fashion using exactly the same amount of fuel.

So do nitrogen filled tire lose less pressure over time? Consumer Reports ran a year-long study to evaluate that very question. They tested 31 tire models, filling one with compressed air the other with nitrogen. On average, the air-filled tires lost just 1.3 psi over their nitrogen-filled counterparts from the initial 30 psi setting. The average tire filled with oxygen lost 3.5 psi, while nitrogen-filled tires lost an average of 2.2 psi over the 12 month test.

What about the claim that the dryer environment inside the nitrogen-filled tire will discourage tire degradation and rim corrosion? There may be some merit to this claim, but chances are that the tread will wear off long before the tire will ever rot from the inside-out. As for rim corrosion, many of today’s vehicles are equipped with aluminum rims that are far more resistant to corrosion than their old steel counterparts.

In our opinion, the most significant downside to nitrogen tire fills is driver complacency. Many car owners may have the impression that once their tires are nitrogen-filled, the pressure levels are now constant and no longer require regular air pressure checks. This mentality is dangerous. A small puncture or faulty valve core can bring about insidious slow leaks that may not be apparent to the driver and the risk is a flat tire or catastrophic tire failure.

Now that service manager may talk a good game, but keep in mind that his shop is looking to justify nitrogen inflation equipment that ran them between $5000 and $20000.

The bottom line is simple. Nitrogen may have some benefits, but they are scant, in our opinion. Good old oxygen, straight from the service station air hose is perfectly fine. Check your tire pressures monthly and you will be blessed with every one of the aforementioned performance, safety and efficiency benefits.