How Much Savings?

I am CoronaCameraMan,

I drove my 4x4 3.7L V-6 Jeep about 75,000 miles from March 2007 to June 2008, I had nitrogen in the tires for all these miles, on level interstate at 65mph in Ohio with no wind I averaged about 18mpg for one tank of gas. I drove coast-to-coast in the US and across most of Canada all times of the year, including a 300km long gravel road.

Interstate highway speeds, engine size and full-time 4x4 probably more then consumed the advantage of having nitrogen in the tires.

My Ford Focus 2.3 L 4-cylinder with air in the tires at 100,000 miles on the clock got 30 mpg driven over the same roads carrying the same load the Jeep did.

I think you'd need to find the average number of under inflated tires on the road and how far the "average" vehicle drives on them each year while being underinflated. Underinflation is most always a gradual process also. How low is low? 3lbs, 8lbs?Plus the average weight of the "average" vehicle and each one's HP rating and aerodynamics. It would be a tall order to accurately estimate all that.................. that said, I wouldn't be suprised at all if tire manufacturers have already computed that along with charts and graphs.

I'd suggest contacting tire companies. Maybe they could give you a reasonable figure for fuel loss at a particular underinflation rate.

I think that 4% rating came from a company that sells air compessors. The one I googled said they make a dual compressor. One hose for nitrogen, and the other for ordinary air............... if I was them, I'd say 5%. ;)

I'd say just check the tire pressure on some kind of regular basis. I think a lot of people only add air when a tire looks low............... and at that point, it's probably been low for quite a while. If the tires were kept properly filled, I can't see any difference between the two.
I do believe I read somewhere that 100% nitrogen expands and contracts less. I'm thinking summer/winter etc. ........that could just be a rumor. I don't know.

The topic of the benefits of nitrogen in tires has been discussed previously. As I recall, the benefits applied largely to racing and high performance applications. The advantages of nitrogen over air for transport purposes were vanishingly small.

On the side of the tire, you will also find the maximum allowable inflating pressure for that specific tire, some tires have a maximum pressure of 32 PSI, some are rated at 44 PSI and some even 50 PSI. Check your specific tire to see what the maximum pressure is for your tires. It is an acceptable practice to have your tires a few pounds below maximum allowable pressure but not too much. Never exceed this pressure.

Lower pressure increases tire heat, infrared photography of tires tested at high speed damaging heat increases as pressure drops. Excessive heat results in tire damage. What we need to know about tires:

1. Date of manufacturing
2. Max inflating pressure
3. Traction
4. Threadwear
5. Max Load capacity per tire
6. Speed Rating
7. Temperature Resistance
8. Tire size

Given that air is ~79% nitrogen to begin with and that the thermal properties of N2 versus air are likely not too different, I fail to see the advantage of using nitrogen in the tires (except perhaps to those who are in the business of selling nitrogen). And then lets discuss the quality of the nitrogen, etc., etc..

The main benefit I see is associated with routinely checking tire pressure. Which is a good idea anyway.

Keeping correct tires pressures serves for fuel savings and tire saving too.

I use to fill my car tires with a mixture of about 79% nitrogen with mainly oxygen and minor portions of noble gases, carbon dioxide and a lot of contaminants aka air.

Nitrogen extraction from air consumes a lot of energy. When considering any process/equipment/technique which promises great money/energy/fuel.... savings the normal way to make any serious comparison is looking the whole life cycle cost, not just a part of it (That's the specialty of marketing people, not engineers)

How much is the fuel savings (if any) for using 100% nitrogen instead of 79% nitrogen?

Compare it with the cost of making an air fractioning plant, plus maintenance and operating costs, plus nitrogen transportation tanks and the fuel needed to distribute the nitrogen, plus.... and surely you'll find it doesn't worth just the time for calculation.

Kind regards

I'm afraid I have to dogpile here;

The only time nitrogen's properties are useful should be when one goes from cold tires to extremely hot tires.

The purpose of tire inflation is to maintain a certain profile of the tire. Since it is external pressure (lapse rate) that causes profile change with altitude change, nitrogen suffers the same profile change as air.

So then the only remaining savings is the temperature change of tire profile. As you have axiomatically stated 4%, we are left with nothing but a 4% fuel savings calculation against world fuel use.

From 2006 International Energy Outlook 2008 from http://www.eia.doe.gov Energy Information Administration

Global barrels used for transportation in 2006:

84979.3921780822

158.987295 liters/barrel = 13510643
4% = 540425L

42 US gallons/barrel = 3569134.

4% = 142765GalUS

Not a dazzlingly large number - but we knew that to begin with, you stated it was 4%.

Personally I think (with no substantiation) that roughly that amount could be saved with proper inflation - sans specialty gases.

Vastly more could be saved by banning two stroke engines used in place of rakes and brooms. Even more could be saved by mandating push lawnmowers.

Not to mention the side benefits of increasing employment and generally improved fitness.

I don't understand how filling a tire with nitrogen would make them ramain inflated longer (as claimed by those who sell nitrogen for tires) than inflating with air. I would think on the whole the average molecuel size in air (average of all the constituants of air) compared to the same volume of nitrogen would be lower for the nitrogen and be able to efuse through the rubber or any small leaks easier.

I think the only difference between air and nitrogen might be a negligable amount of moisture which you may get from a wet air tank or pushed in from a tankless compressor from the moisture in the air. They claim this moisture will make the tires rot from the inside.... I think I am going to wear the tread off the tires before an insignifficant amount of water will make any difference at all.

During the presidential campaigne you remember it was the Messiah who began to tell us that all we had to do was to keep our tires inflated and we can save some monumental amount of oil (daily, monthly, yearly, in a lifetime?). This is BS. First this assumes that every vehicle on the road is driving around on four flats to begin with. It is true that a tire "properly" inflated will have lower rolling resistence than one that is under inflated or flat. By the same token then think of how much oil we can save if we over inflate the tires by 50% or more!

Why stop there - let's encourage the tire companies to develop rock hard tires for cars that are about the same width as a bicycle tire? Think of how much oil we can "save" then!

My point here is, during that this whole idea that we could save vast amounts of oil by simply inflating our tires was speceous. Yes, a low percentage of tires are under inflated but not enough to make make a measurable difference. Think about it..... if everyone aired up their tires tomorrow would some guy who measures oil consumption see any change the following week? Would he say, "Ah Haaaaa! Everyone must have pumped up their tires yesterday!" I doubt it.

When was the last time you checked your tire pressure by calculating your gas milege? Oh - I only got 27.2 mpg instead of 27.6 mpg - I must have a low tire!

I am leery when someone with an agenda (like getting elected) spews numbers and statistics (like creating or SAVING X million jobs - how are you going to measure the number of jobs "saved"?). Similarly, when you hear the greenies tell us that by simply changing to a cork screw light bulb will be like taking 1000 (throw out any number) of cars off the road.....Well that's just great - take 1000 cars off the road for how long? the next 5 minutes? Day? Week? Decade? Forever? (And think what happens when those cars are no longer burning gasoline - tax revenue drops so the tax rate will have to increase to make up for the short fall!).

I will not be hopping on the inflate your tires to save oil band wagon. I already maintain my tire pressure adequately.

Now those cork screw light bulbs is another story. Congress has already seen to it that they will be crammed down our throats and shoved up our sockest in the hear future. They claim massive amounts of energy will be saved. I will be amazed if the amount saved will even be measurable.

Travis

There is no fuel mileage difference directly attributable to nitrogen tire inflation. Nitrogen is only slightly better at maintaining tire pressure than is air, which is, after all, 78% nitrogen. This is effectively a scam, not unlike all the flushes you can buy instead of buying a simple oil change. The 4% figure is ludicrous, that being about the difference you'd expect between tires that spend all their time correctly inflated vs all their time underinflated. Consumer Reports tested a large sample of tires and found that in a year the air tires lost 3.5 psi, and the nitrogen tires lost 2.2 psi.

1. The 1.3 psi difference is not enough difference to have a measurable effect on mileage, even if the owner never checked tire pressures over the course of a year.

2. You should be checking your tires far more often than once a year, and if you do so, and top them up frequently with cheap air vs infrequently with expensive nitrogen, your tires will last longer on air, and your fuel efficiency will be better.

3. The claim often made re oxidation of the inside of the tire is gibberish. The tread wears away long before there is any detectable oxidation damage to the inner liner.