Fuel Economy

If that mechanic had an M.D. degree, he would be called a "quack". Since he apparently lacks that sheepskin, the most polite term that I can come up with for him is Scam Artist. Once your sister realizes that she has blown $50.00, perhaps she will become more wary of obvious scams like this.

No matter what gas is put in the tires, it will not really improve gas milage. My tires are filled with nitrogen only because when I bought them, that is what they filled them with for no "sdditional cost". Taking the lead out of the foot is a sure way to start saving and coasting as much as possible without having to stop is another. Of course, one must stop at the stop signs, but coasting to ths traffic light trying not to bring the car to a complete stop is another way.

The mechanic is probably laughing about what all the way to the bank.

Nitrogen is used in large aircraft because of the change of atmospheric pressure and temperatures. It is a gas that under those conditions is more stable.

"Nitrogen is used in large aircraft because of the change of atmospheric pressure and temperatures. It is a gas that under those conditions is more stable."

Nitrogen is used in aircraft tires because it won't feed oxygen to a brake fire if the tire should explode from the flames and heat.

It is also used in the struts, because it is a stable gas over a wide range of temps.

Nitrogen! Holy Crap! Get that nitrogen out of there before she takes a long trip and blows herself to the moon. I guarantee this will happen when the weather gets warmer. Nitrogen is very unstable when mixed with warm air. And, never go back to that shop again. Your sister is going to someday leave a "Footprint" that is like a moon crater unless you get that Nitro out.
Anyone can improve their mileage by keeping the tires properly inflated. Ask yourself how many tanks of gas will it take, and what kind of driving will she have to do to achieve that $50. I bet it will be insignificant

Did you know air is 80% nitrogen? Many shops install nitrogen now(free) and its safe.

To confirm what andrew j said, nitrogen is safe. You must be thinking of hydrogen. Or nitroglycerin.

I carry nitroglycerin with me everywhere I go. Doggoned heart attack!

Nitrogen! Holy Crap! Get that nitrogen out of there before she takes a long trip and blows herself to the moon. I guarantee this will happen when the weather gets warmer.  

Nitrogen is very safe...Far safer then Normal Air because it doesn't contain oxygen.

However....it will NOT save you on gas mileage...It's a total waste of money. If they offered it for free (like many places do)..then fine..But to pay for it...no way no how.

Nitrogen won't cause anything to "blow up" (unless you put in too much pressure and blow the tire).

Just be sure that you don't use acetylene, though (it's the squatty black tank on your welding truck). Avoid the oxygen, too! If you see the guy roll out two tanks on a dolly, unhook his torch and hook up a filler nozzle, run away as fast as you can. She's about to blow, Scotty!! :D

"Nitrogen! Holy Crap! Get that nitrogen out of there before she takes a long trip and blows herself to the moon. I guarantee this will happen when the weather gets warmer. Nitrogen is very unstable when mixed with warm air. And, never go back to that shop again. Your sister is going to someday leave a "Footprint" that is like a moon crater unless you get that Nitro out."

Norm--Could you kindly cite your source for "scientific" information of this nature?

(I'll save you the trouble. There is no source for this information since you are very mistaken about the properties of nitrogen.)

Norm--Could you kindly cite your source for "scientific" information of this nature?

(I'll save you the trouble. There is no source for this information since you are very mistaken about the properties of nitrogen.)  

Norms scientific knowledge (or lack there of) has been questioned a couple times here.

If the tires blow up from Nitrogen (not possible, but makes for good fodder on this site) she'd save lots of gas because the car WON'T BE DRIVING ANYWHERE!!!!!!!!!!!
Will Nitrogen in my bicycle tires make it easier to pedal up hills?

1. Wouldn't the tire companies be touting this?

They are, at least the questionable ones are.

2. My sister travels 2000 miles a year - how can she save $50.00?

Sure, over the next 50 years.

3. Isn't nitrogen part of a formula for laughing gas?

That is nitrous oxide. Different stuff.

4. Is the "Mechanic" blowing more than nitrogen?

Yea, some oxygen, carbon dioxide and a few other gases. Common air is about 80 Nitrogen. $30.00 is higher than I have heard anyone ripping someone off on this one. Many places do it for free with new tyres. The real cost is a few cents per tyre and unless the pull a vacuum on the tyre to start with they may have brought that 80% to 85%.

Family discussions can get freaky. Overcharging for nitrogen would be $1.50 a tire. $30 for four tires is awful. There is a sucker born every minute. Save nothing, spend $30.

"Mechanic" is a misnomer in this case; ill informed or crook is more appropriate.
Tell your sister to forget this "footprint" garbage also as that ranks right in there with the nitrogen business.

Nitrogen is supposed to cut down on the deterioration due to oxygen inside the tire. It may help some, but that is all it does. A lot of tire companies use this, but the charge should be nominal. It is perfectly safe.

Landfills the world over wish tires would deteriorate. They don't.

They burn well though.

Tires filled with nitrogen will hold pressure longer than with just air. As tire pressure decreases, mileage goes down as well. If your sister isn't good about keeping an eye on her tire pressure, then her fuel economy could suffer a little and the nitrogen would help a little. I'd guess that in a worse case situation, using the nitrogen might save her $5 over a 10 year period, if the "mechanic" gives her free refills as needed, including if she gets new tires.

A couple of issues though, unlike aircraft tires which are purged of air when filling, most tire stores don't do this. They just pressurize the tire with nitrogen, so there will still be some oxygen in there. If you just use air to pressurize a tire and the oxygen slowly escapes, eventually the tires will have a high level of nitrogen, as air is 78% nitrogen.

One good thing about using N2 is that it is dry, no moisture like you usually get from compressed air. Some places use an air water separator on their air compressors, which helps.