Nitrogen in tires

[Martini]

I couldn't find a previous post about nitrogen, but thought the subject has likely been brought up before.

I noticed my local Acura dealer, where we get all our routine maintenance done, has started selling 'Nitro-Safe' for tires. They claim up to 4% increase in mileage, however, I suspect that's probably for SUV tires.

Assuming they only fill the tires to 35-ish psi, would we see an increase in mileage, or would we get better mileage by running air @ 45 or 50 psi? I currently run 50 psi, and don't think the nitrogen would increase my mileage - but I'm curious.

[Armin]

I don't see how nitrogen would reduce friction / deformation losses in the tire (all else being equal). Air is 78% Nitrogen anyhow, so all you are doing is removing oxygen, water and some trace gases. The removal of water might be good for corrosion, but you could do that by just using dry air.

Trucks and race cars use nitrogen to reduce the fire hazard. When a tire catches fire, it'll plow itself out, AFAIK.

[Guillermo]

Tires filled with nitrogen do not change pressure as much as the temperature varies, that's why it's useful for race cars. It also leaks more slowly so it helps maintain proper tire pressures longer therefore increase mileage for most people since they rarely if ever check their tire pressures.

I don't use nitrogen in my tires only because i'm not willing to pay extra money for it, but if it's included with a tire purchase why not.

[JimmyHiggins]

I'll repeat a thing I wrote up at another web board when I heard this Nitrogen thing originally a few weeks/months ago...

So I'm listening to NPR's Talk of the Nation. They are discussing ways to improve mileage. One guy calls and says he's heard that pumping your tires with nitrogen instead of air will improve your mileage.

My brain starts thinking. Why is this wrong? I don't know exactly, only that it sounds fishy.

Then it quickly dawns on me... oh yeah... air is what 78 or 80% Nitrogen to begin with!

So I go to the only place where safe and reliable information abounds... the internet. I find this web site.

Originally Posted by Website linked above

Here are a few other benefits of using Nitrogen in tires:

[1] Nitrogen is denser than Oxygen: This means the larger molecules escape less easily from tires resulting in a more gradual loss of pressure over time. According to the Michelin Tire Manual, a tire that is inflated with Nitrogen loses its pressure 3 times slower than if it were inflated with air.

[2] Nitrogen is moisture free: Pure Nitrogen inflated tires experience less steel belt and rubber degradation. Nitrogen use also reduces valve and wheel corrosion.

[3] Nitrogen provides longer tire life: Nitrogen inflated tire run cooler and require less maintenance according to the Goodyear application bulletin.

[4] Nitrogen is non-flammable: Nitrogen technology has been used in aircraft, military and race car technology for over thirty years.

Well, number 4 had to be the funniest darn thing I've ever read. Who exactly is worried about the air... you know the regular atmosphere that you are already pumping into your tires just combusting spontaneously in the tires of your motor vehicle? If you were really worried about that, Nitrogen may not be safe enough... might need to go with a Noble Gas. Some Krypton may work wonders! They put it in windows after all!

Point 1 above would seem to be the only thing worth noting. However, I'm under the impression that typically air temperature has the largest affect on the pressure in your tires, because the warmer the air, the lower the density, ie the greater the volume a fixed amount of gas fills. I ponder exactly how much research has been done to determine the amount of air that escapes the tire. Yes, the Nitrogen atom is bigger than the Oxygen atom. But let us not get too silly. Might as well use Xenon to fix that problem.

I find the idea that reducing wheel corrosion is a benefit. Typically a tire is done when the tread is nearly gone, not when the tire has rusted away.

This website is mentioning a lot of facts, but not a bunch of actual problems that Nitrogen filling would have on my tires. I'm starting to wonder whether the internet is 100% accurate after all!

But the article continues, and to my greatest relief...

Originally Posted by same article (my emphasis)

The other point to consider here is ‘selling Nitrogen’ is still science – and most people are not that comfortable with the whole science thing. And if you recall I mentioned that regular everyday air is 78% nitrogen anyway – so what would they be paying for?

Regular air is approximately 80% nitrogen anyway, are we to believe that an extra 20% makes all the difference… Ironically we now know that the answer is yes.

Honestly, two points.
1) How is that "ironic"?
2) It is just reassuring that the author says it does make a difference.

Why bother telling the reading how BIG of a difference, when you can just say, well yeah... of course it does. If I lost one pound of weight, I'm sure my mileage would increase in my Insight. Might as well just make that correlation the reason for the new CAFE standards for Detroit (Lose weight!).

Really starting to doubt the accuracy of the internet now. Just one more thing to make me lose it all. Tell me about the author of this online article. I'm sure he knows what he is talking about.

Originally Posted by article - 'about the author'

JAMES BURCHILL is an experienced Internet Marketing & Business Development specialist providing strategic and tactical solutions to select clients seeking to architect their on and off line marketing success.

*Phew*

I can trust this article after all. This guy has a PhD in Chemistry and works in the automobile industry and his accomp... oh wait... he's into marketing?! What the heck?! A guy in marketing is telling me (an engineer) about science and why I should want Nitrogen?

It appears that this article is being written by someone who is being paid to make Nitrogen sound as if it is the end all save all for cars and mileage. What an jerk!

Luckily, I did find a place that was a little more honest about the reality of filling tires with only Nitrogen... ie... it's not anything that really makes a difference.

[Insightful Trekker]

Honda Service News, Sept 06

"Nitrogen Inflation: What's Our Position ?

<huge snippage >
(All the above posts points cover it well)

...Just stick to the air we breathe."

HTH!

[ElectricTroy]

Yeah. Nitrogen.

And while you're at it, pour some Teflon into your engine (slick50) along with a fuel magnet and a cyclone air intake.

(that was sarcasm)

[red1dr]

What gets me about all this is I can't see how you'd get the air OUT of the tires before filling with nitrogen or whatever. You can't pull a vacuum on them. So if you bleed them down to 0psi over atmospheric (which is 14psi) and then pump in say 42 psi (3 atmospheres) more of nitrogen, you still have 1 part in 4 (or 25%) of plain old air, not 100% nitrogen. Am I missing something?

We have lots of nice dry argon in the lab....

[Insightful Trekker]

Your on to one of the "problems" red1dr.

Takes a _lot_ of purging _with_ high purity N2 to result in a tire filled mainly with N2. Else you get a lot of that pesky O2 mixed in there.

I'm sure "they" take it to the Nth ( ) degree with the Space Shuttle. And the NASCAR guys probably rank a close second. But the tire store down the road

You probably get what you pay for (not much of a premimum) and as much as its "worth" in a street car application (again not much). Longer time for pressure loss due to permeation being the only thing I could say in favor of a _high purity_ N2 fill . But you'll _still_ need to check tire pressures as often as recommended. Punctures are _still_ a real road hazard.

HTH!

[JimmyHiggins]

Gosh, I hadn't even thought of the tire having the residual air with all it's explosive oxygen and highly dangerous dihydrogen monoxide. That is hilarious! You'd need a fresh new tube for it to be full of Nitrogen.

I do ponder, will you lose the actual mileage benefit because of the "heavier" Nitrogen atoms?

[Hitokage]

Isn't nitrogen lighter? It only has an atomic weight of 7, while oxygen (which includes even heavier H2O) has an atomic weight of 8.