The reasons for filling your tyres with nitrogen are hot air.
The next time you buy new tyres, you may be asked by the tyre shop if you want them filled with nitrogen. You'll be told nitrogen:
- leaks more slowly from the tyre than compressed air, so you'll get longer tyre life and better fuel economy because your tyres are less likely to be under-inflated
- gives a lower tyre temperature, reducing tyre wear
- contains less moisture than compressed air and so your wheel rims are less likely to rust.
Then there’s saving the planet: a study by Bridgestone (a tyre company) found almost 94 percent of cars in Europe had under-inflated tyres – wasting an extra 8.1 billion litres of fuel every year plus the resulting pollution.
So at a cost of around $5 per filled tyre, nitrogen doesn't sound too bad.
Checking the claims
Unfortunately, these claims don’t stack up. Consumer Reports in the US conducted a year-long trial with nitrogen and found it only marginally reduced tyre-pressure loss. Even a nitrogen-filled tyre loses pressure, which means topping it up periodically – but topping it up with air will undo the "benefits" of the nitrogen already in there. So you'll need to pay for nitrogen top-ups from the tyre shop.
That nitrogen cools your tyres and extends tread-life is also tricky. Cooling down a tyre may give a little more tread life but can also reduce grip – not pleasant to discover when driving on a cold, wet road. Tread is not the only thing holding you on a wet road – the compound of the tyre, inflation pressure and heat in the tyre also play crucial roles.
The argument that nitrogen reduces moisture in the tyre is irrelevant as it’s extremely unlikely that your tyres or rims will fail because of moisture inside a tyre.
We say
- Nitrogen provides some cost-benefit to heavy commercial vehicles and helps stop Formula 1 tyres from overheating. But for the average motorist it provides virtually no benefit, costs money, and may reduce safety rather than improve it. It’s a good way for tyre companies to make a little extra money though.
- Regularly checking your tyre pressures and being gentle with your right foot are our advice for improving tyre life and fuel economy.
More from consumer.org.nz
- Car tyres - test results for over 40 tyres, plus tyre-care tips
Member Comments
Got a question or comment on this topic? Share your views and experiences with other Consumer members...
To add a comment you need to be a member of consumer.org.nz. Login or Join.
Read what our members have to say close
To save money on essentials and make buying decisions easy, you can't go past Consumer. We're proud to have over 65,000 members all enjoying our independent information online or in Consumer magazine.
Here's what some of them say...
"Just wanted to let you know that I find your site excellent! Easy to find my way around, everything at my fingertips - just a click away.
I only took out a 3 month membership as I wasn't sure but it is actually really easy to use and if I want it on paper I can print the
reports. Thanks again".
Denise Watkinson - Waitakere
"My mother (74) got a renewal letter from her insurance company for her car insurance, wanting $570. After reading
your article on car insurance, I contacted one of the companies you recommended, who quoted her $318 for the same
level of cover. I just wanted to stay thank you very much for your article, as it has saved my mother a substantial amount of money".
Adrian Lane - Kapiti Coast
"I've been a member to the magazine since 1997 and enjoy reading it a lot. I've found lots of helpful information on different issues...
Thank you for being so helpful".
Peter Kovalenko - Porirua
"I have been a member of the Consumer NZ for 20 or more years and have enjoyed much reliable advice.
I turn to their tests before making significant purchases".
Lyndal Print – Auckland
Join Consumer now and make your decisions easy on a huge range of products and services
- Over 500 reports, plus interactive tools and calculators
- Independent advice from NZ's trusted source of information
- Join over 65,000 members who help us get all NZers a fairer deal
from just $28
and was a little doubtful to start with however I have definitly noticed improved fuel efficiency.
I paid to get the tyres filled initially however since then I just pop back to the tyre place and they check and top up if necessary for no extra charge. No worries!
I have nitrogen in my tyres have had for over a year, I regularly check my pressure and I have not had to refill/top up yet... I have found that my fuel consumption has also decreased (more km's to a tank)so from my point of view its a winner
You just don't need it. Any more than you need a $32,000 Leica S2 camera to take family snaps at the beach at christmas... The most important thing is to get the subject in frame, focussed and the knobs in the camera on the right settings. Which is just the same with tyres: getting the settings right.
If it is true that putting nitrogen in your tyres does not provide the benefits touted by the tyre companies, then is there room to take legal action under any legislation?
Don't take this the wrong way but that last comment doesn't make sense. The speed of sound in Nitrogen is actually faster than in air. 353m/s as opposed to 343m/s. If your ears are very very special you'll experience those pesky road sounds earlier than in air filled tyres. The article fails to comment on the industry where nitrogen in tyres was first used and also the main reason why. Nitrogen doesn't vary in pressure in relation to temperature as much as plain air. This pressure variation is absolutely critical in commercial Aircraft tyres where they have massive demand over large and sudden temperature variations while landing. In comparison, road car tyres have a very negligible pressure/temperature variance once warmed. The note in the article regarding F1 race cars should really refer to this pressure variance, rather than the consequential overheating.
You have missed the most important reason for using nitrogen in tyres. Nitrogen does not conduct sound, therefore quieter running. Nitrogen injected foams are used extensively where sound reduction is required. The results however will not be the same for all tyres as different munufactures use different componds. If you find there is a lot of road noise from the tyres you have on your car nitrogen is worth a try for this alone. I have driven identical cars with different tyres where one is quiet and one noisy. Nitrogen worked well. Especially for older tyres.
Sorry to burst this, but nitrogen does conduct sound as do all gases. The speed of sound in pure nitrogen is only marginally different (<0.3%) to that of standard air mix assuming the same temperature and pressure. Air is 78% Nitrogen anyway. This sounds like one of those myths that have achieved a life through repetition on the internet and which has nothing to do with actual science. Boyle would be turning over. Might be one for mythbusters...
There is nothing between Nitrogen & Oxygen in the periodic table and they have very similar physical properties. If there was a big difference, the heavier Oxygen would sink to the bottom of the room and tall people would be asphyxiated. The biggest difference is that oxygen can combine chemically with rubber but nitrogen can't. Perhaps that is where oxygen might go (if it indeed goes).
Nitrogen does not cool your tyres! Running them at the correct pressure does.
Air is 1/5 oxygen. If all of this is lost through (or into) the tyre, the tyre pressure will drop by 1/5 (say 30 to 24 psi). When you add more air to restore the pressure you now you have 1/5 of 1/5 of the tyre contents is oxygen. Losing this will drop the pressure by 1/25 (say 30 to 28.8 psi). When we top up a third time you will have 1/5 of 1/5 of 1/5 oxygen. Losing this will drop the pressure by 1/125 (say from 30 to 29.8 psi). Even the pickiest can live with that.
If this isn't just urban folklore, I'll continue to regularly inspect my tyres and don't mind topping them up an extra 3 times over their life (to save paying $5 every time I check their pressures).
One more thing. It is important to check your cold tyre pressure. If your tyres are say 30°C hotter than ambient (perhaps because they aren't properly inflated), their pressure will rise by 1/10 (say from 30 psi to 33 psi). If you let out this extra pressure, your cold pressure will fall to 27 psi. This is enough to affect the tyre's performance and life.
Its the little green valve caps they put on the tyre, they are cute.