I keep 70 some percent nitrogen in my tires all the time…
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You should reward yourself with some 70% green valve caps… 
am I mistaken or have the percentages of gases in the air changed since I was a kid?
It changed. Nitrogen is 78%, oxygen is 21%, and argon is 1%. Ther are several other gases in air, but they are at very low levels. You must be several million years old for it to have changed that much.
Things like this remind me of the Nissan dealer where I used to work and who was huge on selling add-ons at inflated prices. One example…
They charged 249 bucks for a paint protectant. This took their slightly more than minimum wage detail guy about half an hour at most per car with a material cost of about 5 bucks. Do the math.
During negotiations the dealer would halve that paint protectant price and the new car owner would leave feeling that they pulled the deal of the century by getting the add-on for 125 bucks.
The same went for the other add-ons. Even if the dealer halved all of them and the new customer was grinning from ear to ear the dealer was still cashing in big time.
Sometimes the benevolent dealer would even throw the paint protectant in for free… 
Nope, not for the purposes of this discussion. depending on who you read, ambient air varies between about 70% and 79% oxygen. The balance is generally considered to be mostly oxygen with a few percent being argon and all the other gasses combined. The actual mix isn’t really constant except for the purposes of discussion and theory.
Other gasses, such as triatomic oxygen (ozone) have changed. Trouble is, many of our Earth’s protective gasses are affected by not only our presence, but also by things like solar flares and the Earth’s shifting magnetic field (it’s reversing… but not in out lifetime). Brilliant physicists like Neil Degrasse Tyson spend their lives studying these things trying to understand them.
I thought the the reversing of our magnetic field was not something we could predict. how are the holes at the poles these days? I haven t heard much about the ozone layer lately. the sun certainly feels more intense to me, but I know that isn t very accurate.
not so brilliant people like me spend a lot of time thinking about these things too. sometimes I think a good pandemic might be the best thing that could happen to this world and its inhabitants. maybe god could start over with bonobos or gorillas. the chimps seem too much like us, violent and warlike.
So what is the other 22%? Oxygen? Sounds a lot like plain old air to me.
Yup. That’s the joke. Those of us who use “house air” have long been saying that we use 77% nitrogen. Truth is, if you take a tire filled with “house air” from the mounting process, then bring the pressure up to the desired pressure using 100% nitrogen, the original air is still in there… so you don’t have 100% nitrogen anyway.
Wes, the chatter about the ozone holes has disappeared in favor of “global warming”.
The magnetic fields are, according to the astrophysicists, reversing. They estimate that it happens about every 7,000 years, and it’s expected as soon as the next 100 years. Personally, I have my doubts. I spend tons of time reading about these things, 'cause they fascinate me, but I also believe that there’s far, far more about physics that we don’t know than there is that we do know, particularly as it regards the universe. Much of what we believed only a century ago has been proven wrong. And we’re just beginning.
Or you could just sell the customer these, with a fair markup, course . . .
Just as long as you explain to the customer, that they’re not getting nitrogen in their tires, only the green valve caps
And everybody will be happy
The shop will make a tiny profit on the caps
And customer will pat himself on the back, because . . . to the innocent bystander . . . it appears that he his tires are filled with nitrogen
By the way, check this out
https://www.belmetric.com/vscb-black-tire-cap-p-3627.html?cPath=16_155
I was right . . . the green valve caps actually cost significantly more!
LOL, that’s 3-1/2 times as much as a black cap! What a riot!
A dealer, chain, or individual shop can go onto Alibaba and order green caps for a penny apiece; maybe for less if they wanted a full container.
The Chinese are counterfeiting Fender Strat and Gibson Les Paul guitars for 30-50 bucks a pop so their production costs on a measly valve stem cap is near microscopic.
The Chinese seem to have made a cheap version of anything we want and I am not sure that is good. I have 3x of those tire pump up compressors that plug into your 12V cigarette lighter. I had to once use all 3 to fill up one tire. The first one worked but seems to read about 10psi too high. Well, it decided to call it quits as it rattled and ground to a stop so I moved to another one. This one seems to read pretty well on the gage but didn’t work at all this time. I moved onto the next one which worked fine but the gage was broken and reading zero. So, I switched between this one and the broken one with a working gage to finish filling the tire. I was able to repair unit number 2 as a simple wire had broken inside the plug connector and solder fixed it.
I guess this is what you get for buying cheap crap at Wal-Mart. I got what I deserved. All things considered, unit 2 which is the Green Slime brand has done pretty well except for that one incident.
My girlfriend had a low tire and I tried to fill it with her Green Slime brand compressor. It didn’t work so I filled her tire with mine and let her take it with her in case it got low again. I took her old one, figuring it was something simple like a broken wire. It was the exact same problem I had with the connection breaking so I soldered it back together and then swapped back as she liked her model better. We then compared the gages on the units and my unit was reading about 5 psi higher than her’s. I don’t know which one is correct. Now these are all dial gages and not the pencil type but there is obviously a large variance in these too. What is a gage you consider to have decent calibration and quality at the store? Do you have to buy shop grade stuff to get a decent one?
Just an FYI on those cigarette lighter air compressors: Many of them are not designed to inflate a whole tire. They generate a lot of heat, so short duration is what they can tolerate. They are designed to add air to a tire that is already mostly inflated. That includes those sealant/compressor combinations that come OE in place of a spare tire (and wheel).
I am pretty sure my compressors are the kind you mention. I usually try to let them rest between topping up tires as they do get quite hot. Most still seem cheaply made and the fact that the gages seem to lack an accurate calibration is not good.
I bought this one and have been very pleased. Accurate gauge and fan cooled:
I have a Black and Decker Tire Station and it works very well for me. It runs on 120 VAC or 12 VDC. The gauge is accurate, and it has an auto shutoff. Just turn the ring just outside the gauge to the shutoff pressure and go about doing whatever you want. I’ve had it for about 5 years.
Here’s my 2 cents on nitrogen, there is a small benefit and if the cost is free or almost free it would be worth putting it in. But if you have to pay more than a half buck for it, it’s not worth the cost. 99% of drivers don’t drive in such a way that the “benefits” really matter. I check my tire pressure once a month and add or let out air as needed, and even though you lose less nitrogen throughout the month then you do with plain old air, you still need to check, nitrogen isn’t a cure all for low tire pressure.
Now I know of one brand of car (Smart) who’s TPMS is very sensitive and a lot of owners of Smart cars put in nitrogen to shut the warning light off. I’ve been told that a half pound difference is enough to set off the light. In that case it might be worth a buck or two to shut the light off.
“I’ve been told that a half pound difference is enough to set off the light”
no tpms is THAT sensitive. That’s totally exaggerated
if the car calls for 32psi, the light will not come on if the tires are at 31.5psi
Aside from water vapor (very little in air) nitrogen and air are IDENTICAL as far as how they expand with increased temperature. No difference.