Nitrogen in tires


Costco adds nitrogen to my tires. The mechanic says that oxygen permeates the tire walls at a higher rate than nitrogen. It would seem to me that as I add more air to my tire, the concentration of nitrogen would increase as the oxygen would permeate out of the tire at a higher rate than the oxygen. As long as my tire is never removed from the rim or has the air removed from it,over the years I will get close to 100% nitrogen in my tire - so why pay extra for the nitrogen. Please note that air is over 78% nitrogen. Thanks, Bruce


Probably because it is dry. Dry air won’t rust steel wheels.


If Costco offers free nitrogen, graciously accept it. If they try to charge you for it, turn it down. And don’t believe that bunk about oxygen permeating the rubber faster than nitrogen. They have to justify the nitrogen myth any way they can.


They fill the tires with nitrogen for free when you prchase tires from them. Then you can take the car there once a month and or sooner and have them check the pressure and fill them as necessary


Pure nitrogen contains no water vapor. And because of this, tire pressures are more stable under all driving /temperature conditions. So if you have high speed rated tires and operate the vehicle under those conditions, nitrogen in the tires is beneficial. And since there’s no water vapor in pure nitrogen, alloy wheels tend not to leak as easily. And finally, since the advent of tire pressure monitoring systems, nitrogen in the tires will become a standard when filling tires.

But if the vehicle you drive falls out of these catagories, there’s no benefit in using nitrogen in the tires.




Read up on partial pressures of gases. Once you’ve done that you will realize that even if you fill up a tire with 100% nitrogen, the inside gas will eventually look exactly like the air on the outside.


in this case - “eventually” will be a long long time.


Bruce, yours is a great post. You, my friend, are a genious. It’s true, if the difference in permeation were significant then the tires would act like a filter, in essence creating a higher proportion of nitrogen…of course the pressure would go down as the oxygen escaped, but hey, you can’t have everything! And yes, even though you never got to the hypothetical “goal line” you’d keep getting closer and closer over time.

The problem is that the whole nitrogen thing is a farce. The difference is insignificant. How do I know? Simple. I’ve owned cars for 40 years. In all those years the only time I’ve ever had a low tire is when I had a nail or screw…or that big sidewall rip I got from that granite curbstone. And I’ve never had a rusty steel wheel (internally) either.

Besides, does anyone making those claims know how much of the tire is actually comprised of things other than rubber, like steel fibers, kevlar fibers, binders, etc etc, things that oxygen will not permeate? Can anyone making those claims (or anyone else) provide any analytical data that pure nitrogen rather than the 77% nitrogen that is regular air makes any real difference whatsoever? If there is any, I’ve yet to see it.

In short, if they fill the tires with nitrogen as a part of the process at no added charge it’s marketing, but harmless. If they charge you, it’s a moneymaking scam.


The difference is insignificant.

That says it all.