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An engineer says he gets 1-1.5 more miles per gallon with pure nitrogen in his tires. It costs $2-5 per tire to do this.

MSNBC Story (http://www.msnbc.msn.com/id/14121979/)

Ehh...I really don't know about that. Paying $5 per tire to fill up with nitrogen is what I paid for a 12V air compressor that I can use to adjust my pressure whenever and wherever I feel like it, without driving to a tire dealer. IMO their logic is bass-ackwards WRT "resisting pressure change on hot days." According to the ideal gas law, pressure increases with increased temperature. That's good for gas mileage, not bad! It's the other way around: your gas mileage will take a hit in the cold due to reduced pressure. Finally, I don't see any significance to the claim that nitrogen molecules are larger than oxygen molecules. A properly mounted set of tires with no leaks shouldn't lose air, period. I have one tire (previously punctured) that loses 4lb/wk. The other three I haven't touched since June, and their pressure has actually gone up by a pound due to the crazy heat.

Anybody want to take a guess at how much energy it takes to run that nitrogen generator long enough to fill four tires vs. running a compressor to fill them with air?

Call me a skeptic...

The engineer is getting better mileage because his wallet is lighter :D :D

Unless you can get N2 fills free, it's of no use to you.

Maybe I like Red Skelton's (http://en.wikipedia.org/wiki/Red_Skelton) idea of using concrete tires on rubber roads better... :D

Finally, I don't see any significance to the claim that nitrogen molecules are larger than oxygen molecules. A properly mounted set of tires with no leaks shouldn't lose air, period.

I pretty much agree with everything you said except this. Tires are pourous. Air does bleed through them. Just not very fast. In theory nitrogen bleeds slower. I still don't think it is worth it for two reasons.

1) Air is cheap ($.50 is the most I've seen a pay pump cost)
2) It leads to complacency. If someone uses nitrogen because they feel they don't need to put air in as often, they might also feel that they don't have to check their tires that often.

Hi Chuck:

___This is the kind of news item that really gets to me … If this so called engineer gets 1 - 1.5 more mpg from N2, imagine the 30% increase he would get with a Turbonator! How about the 25% increase he would get with the gasoline ionizer? 10% by using Acetone … Keep adding up the gimmicks and pretty soon this “Engineer” wouldn’t be using any fuel at all! Sad commentary about the press when this kind of reporting is allowed to go unchecked let alone coming from a guy that is receiving a lousy 20 - 22.5 mpg’s from a Chevrolet Colorado P/U truck rated at 19 city/24-25 highway depending on Stick or Auto tranny …

___Good Luck

___Wayne

I saw a story about this on msnbc.com yesterday. I thought,,, here we go again.

Have to confess when I see this thread I read nitrogen as "helium" and the idea of putting that in your tires for FE gives my brain a tickle.....(sorry, must be that extra 'x' chromosome)

Speaking of helium, say you have a big bladder in your trunk connected to a helium tank and a compressor. When going uphill, you let the helium out of the tank into the bladder and fill your trunk with helium, displacing the heavier air, thereby making your car lighter, making it easier to climb the hill. While going downhill, you turn on the compressor and pump the helium back into the tank, making your car heavier, giving you more momentum downhill. I wonder how much FE that is worth....:p

I would try this before I put nitrogen in my tires.:D

I think you can even buy helium at Walmart.:p

I think I'll get some of that N-Stuff. :Banane45:

tiger

BTW, maybe :rolleyes:

The main advantage of filling tires with nitrogen is that it is dry. If you're using a home compressor or using the gas station's compressor, you are putting water in your tires. Depending on how often you do this, you can add quite a bit of water to tires (ask a tire guy, they've seen literally cup(s) full of water in each tire at tire change.

More than anything, the water will throw off your tire's balance. Not to mention, the degrading effects of water on the tire/rim. Plus it stinks real bad when they break down the wheel assembly at tire change.

Most good tire shops are now using nitrogen, and I know my tire shop doesn't charge an extra price (it's built into the cost of the tire)

Nitrogen is cheap, go for it!

Andy (a more positive fellow thanks to xcel)

The article mentions that NASCAR and big-rig drivers are fond of nitrogen. Heat build up on long trips might be a concern for some of us, although my wheels did not feel real hot travelling during HybridFest.

I'd due to replace my tires early September to pass inspection, so I'm definitely not doing it before then....

Air is about 80% nitrogen, so I wouldn't sweat the difference.

The water in the tire thing is an interesting point that I hadn't thought of. I bet it's darn near impossible to get it all out without removing the tire from the rim, too.

Note to self, don't fill on humid days!

Andy. Thanks for pointing out the water thing. If I can get a tire filled with nitrogen at a price lower than a non filled one I'm not going to say no. I just don't think it is worth paying extra money for it.

Have you seen any badly corroded rims due to water being inside from filling with air?

The main advantage of filling tires with nitrogen is that it is dry. If you're using a home compressor or using the gas station's compressor, you are putting water in your tires. Depending on how often you do this, you can add quite a bit of water to tires (ask a tire guy, they've seen literally cup(s) full of water in each tire at tire change.

More than anything, the water will throw off your tire's balance. Not to mention, the degrading effects of water on the tire/rim. Plus it stinks real bad when they break down the wheel assembly at tire change.

Most good tire shops are now using nitrogen, and I know my tire shop doesn't charge an extra price (it's built into the cost of the tire)

Nitrogen is cheap, go for it!

Andy (a more positive fellow thanks to xcel)

Hi Andy,

Nice to see a "Mix" here, I see you have a 04 TDI Jetta. I have driven them as well as several TDI Bettles with the DSG Trans. I likeee. :D

Say I'm sure it has been said, but here goes again.

:D Welcome to CleanMPG :D

tiger

I just wonder how he figures 1-1.5MPG improvement.

If I put a plastic religious figure on my dashboard and notice 1 or 1.5MPG difference should I say God is paving the way, or just figure luck?
-Steve

Air is about 80% nitrogen, so I wouldn't sweat the difference.

78.1% N2
20.1% O2
0.8% trace gases like Argon, Neon, Carbon Dioxide, Helium, Krypton, Methane, and Hydrogen.

/pedant :D

I've claimed that just after a fresh rain, the waper vapor has improved my mpg, and it's one of those maybe it does, maybe it does not issues....

exerpt from http://www.msnbc.msn.com/id/15496174/

Nitrogen is “a safe alternative” to normal air, says Dan Zielinksi, a spokesman for the Rubber Manufacturers Association. Because it’s an inert gas, it won’t catch fire. That’s why it’s used in airplane and race car tires.

Nitrogen does appear to have a genuine user benefit for passenger car tires — it does not seep out as quickly as compressed air. Robert Moyer, who heads Costco’s tire division, tells me their tests show air migrates out of tires “three to four times faster than nitrogen.”

Remember, to maintain this benefit these tires must only be topped off with nitrogen. Jennifer Stockburger, a senior automotive engineer at Consumer Reports, points out that once you add any air “you have essentially contaminated the nitrogen inside and reduced its benefits.” That’s why nitrogen-filled tires have a green valve cap.

Having your tires filled with nitrogen does not mean you can skip the monthly check to make sure they are properly inflated. A slow leak can drop the pressure 50 percent, and you wouldn’t know it by just looking at the tire.

I'm still not realy into nitrogen. It seems to me that if you have to check them anyway why not just top them off when you do.

The 1st paragraph of the quote suggests that nitrogen would benefit most those going at high speeds. That does not apply to most of us.

Hi Chuck:

___I have been doing fine on regular air instead of purified air for the last 26 years. N2 in your tires adds nothing except for lower fuel economy because it does not expand as much during heat up. Why bother …

___Good Luck

___Wayne

Sorry if it seemed I was serious about this. Happened to run across that blurb at MSNBC.com and it seemed more intelligent than you average post...

78.1% N2
20.1% O2
0.8% trace gases like Argon, Neon, Carbon Dioxide, Helium, Krypton, Methane, and Hydrogen.

/pedant :D

I like trace gases. I can draw really well with a good trace. :p

There are many articles about what a larf it is to go with Nitrogen in your tires as being the best way to lighten your wallet and do little else.

Heck, when I got my tire repaired and a screw taken out that I had run over not that long ago, there was an article at the tire store about not getting Nitrogen in your tires; that it's really not worth it.

O.K. Maybe I'm a sucker but, I did have my new set of RE92's filled to 60psi with N2 a couple of weeks ago at installation. (at $5 each) I even had to drive 80 miles one way to get N2 installation. I did it for the stability factor. I have ran 60psi air in my tires for the past 1.5 years and 50,000 miles. This summer on a week that the temps went from 70's to the 90's I found my tires at 70 to 73 psi. I had been driving on them at that pressure for a couple of days. 60 psi is pushing the limits. 70+ is too much for sure. Yes, I think the mileage claims are ficticious. I was asking the store manager about N2 sales and he said a lot of people were requesting it. He said his father's Honda Accord increased 1.5 to 2 mpg after installation. Yeah, right!

But at higher pressures, leak down is a problem as well. N2 molecules are much larger.

Temps are now in the 40's to 20's. I'm going to check the pressure this weekend to see how much of a psi drop.

If the N2 molecules are that much larger, won't they accumulate
in a tire filled with air that then slowly leaks out the smaller
molecules, thus increasing the concentration of N2 over time as
you keep pumping in a little more 78% N2 mix every time you top up?
.
_H*

This is what I think of it.

I have the nitrogen tank, regulator and vacume pump to do it. And it aint worth the effort.

Hi Msirach:
This summer on a week that the temps went from 70's to the 90's I found my tires at 70 to 73 psi. I had been driving on them at that pressure for a couple of days. 60 psi is pushing the limits. 70 + is too much for sure.
___70 is not too much by a long shot! You just have to believe what I am telling you as I promised never to divulge the burst pressures of Bridgestone’s as I was speaking with one of the head Bridgestone engineers in person earlier this year.

___Pressures above 60 add little to no increase in FE so any more adds nothing. Running above 60 because of heat up is not a problem. 60 - 65 is a normal range after heat up and I am pushing 65K on the Michelin MXV4 Pluses on the much heavier Accord. Recommendation, run MAX sidewall. Anything more is up to you ;)

___Rule of thumb is ~ 1 # drop or rise for every 10 degrees F drop or rise. A pressure gauge or PV=nRT would nail it down though :D

___Good Luck

___Wayne

Hi Msirach:

___Something I hope helps?

Driving Under Pressure - Proper Tire Pressure Could Save Your Life (http://www.officer.com/article/article.jsp?siteSection=19&id=27281)

___Good Luck

___Wayne

For whatever it's worth, I broke out the science and commented thoroughly on this topic several times in the following threads. I was a bit annoyed at all the false information in the "fill your tires with nitrogen" websites.

http://www.greenhybrid.com/discuss/nitrogen-in-tires.8995.html (http://www.greenhybrid.com/discuss/nitrogen-in-tires.8995.html)

http://greenhybrid.com/discuss/showthread.php?t=7654

I think that for most, any benefits of filling with nitrogen are negligible.

Hi Mr. Kite:

___It was not just the N2 Fill web sites that keep this kind of non-sense alive. Being perpetuated by new Hybrid and non-hybrid so called “Hypermiling experts” (that being mentioned hysterically :D) is a travesty to all. Some hybrid sites have a lot of those types ;)

___Good Luck

___Wayne

what's a PV=nRT?

what's a PV=nRT?

It is the Ideal Gas Equation.
P = pressure
V = volume
n = number of moles
R = constant
T = absolute temperature

Just as Kite says. To use this to determine the pressure in your tires at different temperature, simply realize that V, n and R are constant and so P is directly proportional to T. Now just remember that T here is absolute (as he also said), and 70 oF is 546 o absolute (hope I did that right). Now for example 100 oF is 576 absolute, so the pressure increase moving from 70 to 100 oF is 576/546 = 1.055. So Dr. Avogardo says your tire pressure will have increased 5.5%.

If water vapor pressure varies more with temperature, I believe that would have to do with the liquid to gas phase change; outside the scope of the equation.

DAS, gettin' by with compressed air.

Hi Tochatihu:

___Bring out the steam tables ;)

___Good Luck

___Wayne

The temperatures need to be in Kelvin or another absolute scale.

70F = 21C = 294K
100F = 38C = 311K
P2/P1 = T2/T1 = (311/294) = 1.058 (an ~6% increase)

That's about the same as you got, but I am not sure what temperature scale you are using.

To go from Celsius to Kelvin, you just add 273.15 to the Celsius number. (The degrees are the same size, but are offset.)

Temperature Calculator (http://chemistry.about.com/library/weekly/bltempconvert.htm)

[QUOTE=xcel;15175]

___Bring out the steam tables ;)


When I think of steam tables, buffet lines come first to mind.

DAS

When I think of steam tables, buffet lines come first to mind.

DAS

:D

___Good Luck

___Wayne

A couple more thoughts:

Why don't we just contact www.snopes.com (http://www.snopes.com) on this urban myth?
A can of Fix-O-Flat might be more effective in keeping tires sealed for possibly less money.

It was suggested that Fix-o-Flat is going to make life hard at the tire shop...