What would be the reason inflating your tires with nitrogen would produce better fuel mileage?

Question

A friend of mine got a flyer from a car dealer suggesting this. I've heard of filling tires with nitrogen to prevent dry rot during long periods of storage but why would it produce better mileage? Less rolling resistance being more dense? Different temperature coefficient? There has to be the actual answer somewhere but all I can come up with are half a**ed guesses.

I do have access to nitrogen so cost is not a factor

Answer 1

The biggest winner is the Car dealership who sells and services your tires. Otherwise it is an Urban Myth that Nitrogen will do anything that regular compressed air has been doing for the last 100 years. And I like many of the answers below. Let us know if Nitrogen is right for your tires But unless you evaculate the tire to 30 inches of vacuum before filling all that space inside the tire will still be filled with oxygen.

Answer 2

Mostly it is a scam to some degree. The nitrogen does have larger molecules and that will prevent the tire from losing pressure longer. I have heard that race cars use nitrogen to keep the pressures more consistent. When the tire gets hot, the nitrogen will not expand and increase pressure.

So unless you are planning on running 500 miles at 200mph then I don't think it is worth the $7.50 a tire they charge around here to have them filled.

I would just as soon, add some air before I go on a long trip, or add some air if the tire looks low.

It doesn't hurt anything to have the nitrogen, but why really? The $30 bucks plus tax can be used for other things like a case of beer while you air the tires up. lol

Answer 3

Accornding to several studies I've seen it makes no difference. You still are suppose to keep checking your pressure regularly. Regular air you breath is something like 60 or more percent nitrogen as it is. The nitrogen people, and the tire shops would like you to think there is some value though - go figure.

Answer 4

Research this more. I have a problem with the other answers because:
Air consists of 78% nitrogen, 21%oxygen, 1%trace elements including CO2.
Oxygen is the only thing that might have any effect on the rubber (or synthetic materials) tires are made from.The actual weight of the gasses and thier properties are negotiable. Is it worth the expense to get pure nitrogen pumped in or loose the $1 in gas over 10,000 miles if it has any effect at all?

Answer 5

the tires maintain their proper pressure for longer periods of time due to the fact that nitrogen molecules are larger and are less likely to escape through the tire than ordinary air. If you maintain your tire pressures regularly then you won't have to pay for the unnecessary expense of nitrogen. Besides what happens if you get a flat, will the repair shop have a nitrogen filling machine?

Answer 6

Even though:

"O2 "permeates" approximately 3-4 times faster than does N2 through a typical rubber, as is used in tires, primarily
because O2 has a slightly smaller effective molecular size than does N2."

source: http://www.getnitrogen.org/pdf/graham.pdf

That does not explain the claim of better fuel mileage. I believe one person was on the right track. It does have to do with the molecular mass of oxygen being higher.

The mass of the gas in a tire with normal air is 26 grams.

Source: http://www.madsci.org/posts/archives/2001-08/998945256.Ch.r.html

Mathematically we can calculate the difference. Nitrogen gas is 28 grams per mole. Oxygen is 32 grams per mole. There is 80% N2 and 20%O2 in air. That makes average molar mass of 28.8 grams per mole. at 26 grams this equates to .90 moles of gas. At 20% that is .18 moles of oxygen. That means 5.8 grams is oxygen. .18 moles of N2 would weigh 5.0 grams. That is .8 grams difference!

Although this is a ridiculously small amount the claim is valid(mathmatically anyway). It does require less energy to spin identical tires inflated with nitrogen, but such a negligable amount. So negligible that cleaning your rims would see higher gains.

Answer 7

wow, air is most nitrogen all ready. look that up ok?
air planes use it for fire safety.
ever see the big brakes on 747? like barbeque!

it doesnt do a thing for you , its just another silly way to take your money.
If you do a search you can find this out for your self.
find someone that can prove it.
with real tests and real proof and not stupid testamonials.

buy a cheap air compress and fill them every 2 months.
now you have something that is good for other things.
like air tools, paint gun, etc.
not someworthless Nitrogen tank.

DRUM ROLL:
the real truth:
I've convinced myself the biggest cause of pressure loss is the gas you lose every time you check the pressure.

BELEIVE IT>

Answer 8

As one person pointed out, you won't have any air pressure loss. You won't have any air pressure loss because if you fill it with Nitrogen, there won't be any air in the tire to lose.

Nitrogen is slightly lighter than Oxygen, but as someone pointed out, most of the air we breath is Nitrogen, I think the lightness factor is slim.

I think it's one of those myths like putting acetone in your gas tank will give you better gas mileage.

Answer 9

Nitrogen changes volume less with temperature changes, therefore a properly inflated nitrogen tire will spend more time close to it's optimal operating pressure than a tire inflated with plain old air.

It will not leak any less.

Answer 10

The tires stay at optimum pressure during conditions like weather change or high sustained speeds...

This allows for the tire always give maximum efficiency and in turn less friction.

In cold weather tire pressure can drop.

Softer tires create more friction.