My wife and I bought a new 2024 Mazda CX5 Carbon addition car late last year.
One of the things I noticed but never gave thought till now was the green caps on the tire valves, meaning they are Nitrogen filled.

Is there an advantage to Nitrogen filled tires? If the pressure is low can I put air in them or does it need to be just Nitrogen?

I know the dealer does Nitrogen but is there some ware I can buy Nitrogen and store it at home if needed?

This is all new to me so any help is appreciated.

Thanks

All the advantages of Nitrogen in a tire are wasted on a car. It won't hurt anything but your pocketbook, but it won't do you any real good either over standard air from a gas station. It's a convenient way for a dealer to upcharge you though for something you don't need. A plane's tires or land speed record attempts can take advantage of nitrogen's properties in a tire, but not a typical automobile. Your tires are not going from 0 to 200mph instantly like a plane's tires or over 150mph ever..

Normal atmosphere is 78% nitrogen, so the question becomes, what advantage is there to buying 22% more nitrogen from a dealer?

None other than adding to the stealership's profit margin. I saw a local Toyota dealer advertising filling 4 tires with nitrogen for $100.

Adding normal air to a nitrogen filled tire is no issue at all.

It's just a monetary advantage for the dealer, in my opinion.
Supposedly the tires will not lose pressure as quickly (it's the oxygen that can slowly go out through the rubber), but is that really an issue for anyone that maintains their car?

No advantage to it for normal passenger vehicles. If offered free, say with a purchase of a set of tires, OK, but don't pay extra for it.

It's like letting the quick lube place change your air filter or wiper blades: ridiculous markup for them. Don't bother unless it's free (I think some places like Costco will refill with nitrogen if you bought your tires from them).

Main benefit is temperature stability over normal NOX mix of the atmosphere. Why? Nitrogen itself is more inert but mostly because there's zero moisture in the processed nitrogen over what a normal compressor can do by intaking ambient air.

Pro-tip; your local Costco typically has a nitrogen filling station in the parking lot for members. No, there's no check on using it.

Race wheels have two valve stems....purge all ambient air out and fill with pure nitrogen to make tire pressures more controllable. Mostly a waste on a passenger vehicle as Boyle's Law still applies

The rate of loss of air over nitrogen is a bit less than 4%.

That loss is negligible compared to the variable of loss due to individual tire construction and permeable rate, bead leaks, leaks due to cast wheel porosity, and valve stem leaks.

Or as some my betters used to say. "Bupkis!"

We used it on aircraft tires because it is more stable pressure over temp changes from 100 plus degrees on the ramp and even higher temps on taxiing and takeoff when heaviest and extreme rolling friction/flexing, and then after hours at -60 cold soaking at altitude and then landing.

Both extremes with air prove catastrophic failure do to over inflated and underinflated at the most extreme ends of aircraft operation for tires.

Thank you for the information everyone it was very helpful.

The Nitrogen filled tires came with the car from the dealer. I don't remember if it was factory installed or dealer installed along with the locking lug nuts and window tint.

Whenever we buy a car that does not come with a "free" service plan (oil+filter change, tire rotation, road side assistance and topping off all fluids) we buy it during the up sell at closing, it's the only thing we have purchased in the past.
My wife figured it out financially that it works in our favor, she has done the math.

As part of that the dealership is also suppose to make sure the tire pressure is correct and if not they are suppose to top them off, hopefully with Nitrogen. I am going to check next time we are at the dealership.

My concern was can some air be mixed in without it being any kind of problem for that one tire.

In central Florida during the winter months it can get very cold overnight, for Florida. I walk my wife out to the car every morning when she leaves for work.

On more than one occasion the tire light on the dash comes on because the cold weather drops the tire pressure just below what the tire pressure sensor is set for.

So out come the 12 volt pump to fill any tire that is a little low.

Once again thank you everyone.

Profit builder for the dealer.
No practical value for a consumer.

My limited understanding is that oxygen permeates tire rubber sidewalls faster then nitrogen, with the implication that you might loose tire pressure slower with pure Nitrogen than with straight air. But I don't know how much of a real affect that is, but I'm pretty sure it's nothing of real value for daily driving or street racing (whatever the hell that is, but basically illegal driving, aka high performance driving by unqualified drivers).

The first link describes the physics of nitrogen vs air in tires:

https://www.getnitrogen.org/pdf/graham.pdf

The second link describes the reason Nascar puts Nitrogen in tires instead of air:

https://flowracers.com/blog/nascar-nitrogen-tires/

After reading those two articles, it's clear to me that any legal driving on regular public roads with any kind of street legal car with Nitrogen in your tires is like wearing a Toupee in a bar to pick up younger women, and if the young woman turned out to be a Nascar driver and she heard you put Nitrogen in the tires of the car you drove to the bar, that could be a good snl skit.

On the other hand, this is America, and you can put whatever you want in your tires. I met a man once who put water in his big truck tires, something to do with tractor pull or mud racing or some other redneck something or other like that.

My guess is that if you're concerned about watching your tire pressures, which I do myself, my experience is that by using top quality tires like Michelin, excessive air leaking is non-existent for all practical purposes, assuming you have a good wheel with a clean properly shaped factory bead on your wheel, and you aren't pushing any boundaries with the tire width and aspect ratios for the particular wheel you are using.

That's just for driving on roads, I'm not an off-road person and all that.

I delivered Nitrogen to Wright Patt, CVG, and Airbourne for aircraft, for cars it's a scam.
If the temps get cold just add a few PSI.
I may be wrong and if I am someone tell me, I think the Navy used helium instead of Nitrogen.

quote:

Originally posted by 71 TRUCK:
In central Florida during the winter months it can get very cold overnight, for Florida. I walk my wife out to the car every morning when she leaves for work.

On more than one occasion the tire light on the dash comes on because the cold weather drops the tire pressure just below what the tire pressure sensor is set for.

That won't change with nitrogen filled tires, it's a function of the temperature that the tire was at when it was filled last.
If you watch the TPMS (tire pressure system in your car), you'll see the pressure increase as you drive - the tire gets hotter, the air inside gets hotter & since it is contained, the pressure goes up.
Conversely, if the shop was 90* when the tire was installed, what do you think will happen when it's 40* outside overnight? Pressure will drop ~10%, air or N2. TPMS will trip the light if there's more than 2-3psi difference between high & low of the set.
Gas law:
PV=nRT V, n & R will stay the same -> T(emp) goes up, P(ressure) goes up too.

quote:

Originally posted by 71 TRUCK:

My concern was can some air be mixed in without it being any kind of problem for that one tire.

Absolutely no problem at all for a commuter car, driven at city and highway speeds. The tires won't know whether you fill them with ordinary old compressed air, or nitrogen.

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I use a 78% nitrogen blend in my tires.

Paying for N2 fill? Nope! Using Costco’s free N2 fill machines to top off when there? Sure. There is no disadvantage to filling with Nitrogen, but there isn’t enough of a benefit to justify paying anything for a nitrogen fill on typical passenger car tires..

Number one rip off by car dealers, followed by window etching, fabric and paint protection.

I have nitrogen bottles at work.
All I would need to do is let the air out of my tires and fill them back up.
Not doing it.

quote:

Originally posted by PGT:
Race wheels have two valve stems....purge all ambient air out and fill with pure nitrogen to make tire pressures more controllable. Mostly a waste on a passenger vehicle as Boyle's Law still applies

My understanding is that race car tires have an "inner liner" that separates a higher pressure inside compartment from a lower pressure tread volume. This is to more closely control the size and shape of the contact patch. It sometimes happens that these two compartments equalize (e.g. via a puncture in the membrane between them), and performance suffers as a result. This is why there are two valves, not for any "purging" procedure.

And, as noted in other posts, using nitrogen is to eliminate variances caused by the water vapor in air. Not a factor in typical off-track driving profiles.

quote:

Originally posted by slosig:
Paying for N2 fill? Nope! Using Costco’s free N2 fill machines to top off when there? Sure. There is no disadvantage to filling with Nitrogen, but there isn’t enough of a benefit to justify paying anything for a nitrogen fill on typical passenger car tires..

This is what I do because I get my gas from Costco; no lines, low price, easy to deal with. The nitrogen filling stations are nearby and I periodically check my tires and refill if necessary. Never paid extra for nitrogen tires or anything.

I have summer air now till October then I put in winter air till May.