Nitrogen in car tyres latest evidence that marketers believe a fool is born every minute

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Motorists are being urged to pump up their car tyres at $20 a pop with nitrogen rather than ordinary air. Is anybody else reminded of the expression: “A fool and his money are soon parted”? And the famous dictum: “There’s one born every minute.”

The air that we breathe, and which is compressed into car tyres, is 78 per cent nitrogen, which is colourless, odourless and inert. The skeptic might well ask what the point is of filling a car’s tyres with 100 per cent of it in place of the 21 per cent which is oxygen and the 1 per cent that is everything else.

Pure nitrogen is used for jet aircraft tyres, because it makes the tyre insides perfectly dry. Moisture can freeze in ordinary compressed air at the high altitudes jets fly at, causing balance problems on landing. Racing car tyres are also filled with it, as the slightly smoother ride that results can make all the difference in a race. But ordinary road cars?

Promoting this joke is Firestone. Its website publicity says: “Filling your tyres with nitrogen is a good way to get better performance and safety from your tyres. Nitrogen will leak three or four times more slowly than compressed air, which can lead to some pretty useful benefits like stable tyre pressure, improved road grip, safer all-weather performance, increased fuel economy, no internal oxidisation through the elimination of moisture [and] increased tyre life.”

Surprisingly, the New Zealand AA website has nothing about the merits or otherwise of nitrogen, only a mention that AA Rewards can be used pay for nitrogen from Firestone.

A search of automobile association sites overseas turns up plenty of references. Typical is the United Kingdom AA, which says: “The advantages of using nitrogen in specialist applications are clear [but] while accepting the possibility of purified nitrogen being of benefit in certain applications, we don’t think that the cost and possible inconvenience are justified for normal passenger car use.”

It adds: “Changing to nitrogen involves removing all the air which is already in the tyres and then re-inflating them with purified compressed nitrogen. There will be a one-off charge per tyre but once filled with nitrogen any future top-ups would also have to be with nitrogen if any advantages are to be maintained.

“For passenger car applications, the main claims seem to be reduced corrosion, because unlike air, there’s no moisture in pure nitrogen [and a] slower rate of pressure loss because nitrogen molecules are larger than oxygen molecules (which make up 21 per cent of compressed air). Leakage can occur through the tyre’s inner liner but can also occur through the valve, punctures, or failure of the seal between tyre and wheel rim. Pure nitrogen might leak more slowly through the liner, but regular checks of tyre condition and pressures will still be essential. Corrosion of the tyre through use of normal compressed air alone is most unlikely because only the outer tread band of a car tyre contains steel. The amount of moisture reaching it from the inside is minimal.”

That seems clear enough, and from a reputable source of motoring advice.

Kiwi online commentary pioneer Bruce Simpson, who has run the Aardvark website since 1995, is scathing in an article published yesterday under the headline Snake oil in your tyres.

Bruce writes: “Has Firestone breached NZ’s rather stringent laws in respect to making claims that can’t be substantiated? Well it’s a bit tricky I suspect. Since all the claims made for nitrogen have some substance in theory, it can’t be said that they’re not true. However, I think the key issue is whether customers will actually see these claimed benefits in practice – which I strongly doubt.”

And Bruce adds: “But this has to be very close to a scam… If it’s an amazing product that improves fuel-economy you’re after, I could sell you some great car polish. It will reduce your fuel consumption and increase your top speed – the science proves it. However, just like the nitrogen fill, the difference is so small for the average driver that you’d never notice the difference. Nitrogen, polish, snake oil. Spot the odd one out. There isn’t an odd one out.”

You have been warned. Don’t be a fool. There are many better things to spend your $20 on than stuffing nitrogen in your tyres.

Hat tip:Aardvark.

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Filed under Consumer issues, Skeptical, Transport

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