I have had to lower my estimate of the quality of LiveScience.com. It is generally a straightforward science news outlet, but some recent articles have shown me that they have an insufficient filter in place and need more quality control. The worst abuse is their Top Ten Unexplained Phenomena (I’ll tackle that next week).
A more subtle problem, however, are articles that sound superficially reasonable but are actually just thinly disguised advertisements. Even more insidious is the habit of reprinting press releases without doing further investigation. This is an easy way to bulk up an online news feed. Some sites do nothing but aggregate press releases – and that’s fine, as long as it’s obvious that is what’s going on. But many sites also reprint press releases as if they were written by a science news reporter. Press releases are not always the most objective or even accurate reporting on a scientific discovery.
This article from LiveScience seems to be one that was spoon-fed to the reporter, Trey Granger, who did not give any evidence of doing any independent digging. The story is about filling tires with purified nitrogen instead of regular compressed air to improve gas mileage and extend tire life. Granger did not question any of the claims of the company selling the nitrogen system – the readers who left comments did a better job of asking questions.
There are several approaches to a claims like this – common sense, testing the underlying claims, and testing the net effects.
From the common sense point of view – how do the claims jibe with logic and basic scientific facts – the claim that purified nitrogen in tires will make a significant difference seems dubious. Air is already 78% nitrogen, the rest is oxygen with some carbon dioxide, water vapor, and then trace gases. The specific claim is that oxygen leaks out of tires faster than nitrogen. This may be true, but it seems unlikely to be significant.
Let’s take a look at some of the specific claims in the article:
1. Nitrogen makes up almost 80 percent of our air, making it a naturally-occurring element that we’re exposed to every day
2. Because it is a dry gas, nitrogen is more stable than oxygen and will cause less leaks and rust
3. Nitrogen lasts longer in your tires (up to six months without a top-off), allowing you more leeway with tire pressure
4. You can expect up to 30 percent better tire wear if they are properly inflated with nitrogen, meaning less tires to dispose of (use Earth 911 to find out where to recycle tires near you)
5. Nitrogen can also be used to fill non-car tires, so you can improve the life of bicycle and motorcycle tires
You see how it reads like an advertisement, not science reporting. Nitrogen is naturally-occurring? First – so what? Second – so is oxygen. Nitrogen is a dry gas? What does that mean? Is this a clumsy way of saying that purified nitrogen has the water vapor removed? Three and four are the actual claims (the first two were just lame sales-pitches, the kind of dubious things that companies use to increase the list of supposed benefits of their products). And five, again, is just a sales pitch.
What about the actual claims? The first claim is that nitrogen lasts longer in tires than regular air. This is not an end in itself but is the supposed mechanism by which cars will get better mileage and have longer lasting tires. This claim was tested by Consumer Reports. After one year they found that tires filled with regular air lost 3.5 psi from a starting point of 30psi, while nitrogen filled tires lost 2.2 psi. That’s a difference of 1.3 psi over one year – which hardly seems significant.
The report of the study left many questions unanswered, such as how the tires were used over that year, if at all, but I did note that Consumer Reports filled and emptied the tires with nitrogen three times and then measured the nitrogen to make sure they had 95% nitrogen. This is a good method to test the effect of 95% nitrogen in the tires, but it may not be a good test of the real world use of nitrogen tire filling systems. I doubt the average user, even at a garage, will be so fastidious.
The removal of water vapor, according to all the car sites I checked, can reduce the expansion and contraction of the air inside the tires with heat and cold, and therefore maintain more even tire pressure. This can matter to a race car, where minute changes in tire pressure will alter the handling of a high-performance car racing at tremendous speeds around a track. This is insignificant to a consumer on the road.
What about the net effects of this small advantage to nitrogen (assuming the Consumer Reports tests are accurate)? The New York Times did an article on this question – this was not a formal study but a informal trial conducted by car dealer, Earl Stewart, who used the nitrogen system for eight months in some of the tires he placed on his cars. He found minimal differences in wear and tear on the tires, and switched back to regular air.
The Bottom Line
Pure nitrogen in car tires seems like a waste of money and probably a net disadvantage. It costs about $10 a tire when purchased to have them filled with nitrogen. If you want to keep them filled with nitrogen you then have to find a shop that has the equipment, or you can purchase the aerosol refill cans – adding extra expense.
The advantages to tire pressure are insignificant to the consumer driver on the road. In fact, I think such a system would be a net negative, and here’s why. Far more important than what your tires are filled with is that they are kept filled. Keeping tires properly inflated can improve gas mileage, on average, about 10%. This is far more of an effect than all the so-called green technologies that are increasingly popular.
Filling one’s tires with nitrogen may lead to a false security and therefore decrease vigilance about checking tire pressure. Also, difficulty in finding a station to refill the tires with nitrogen may delay refilling the tires – it can be an unnecessary barrier to filling tires properly.
Tom and Ray over at CarTalk (I love those guys) say:
So, none of these advantages is important to the average driver. They just don’t matter enough to ever think about. And they certainly don’t matter enough to pay for, Rob.
(They were answering Rob’s question)
Nitrogen for tires seems like a overly complex and expensive solution to a problem that is much more easily, cheaply, and effectively fixed by simply checking your tire pressure regularly. In fact, checking your tire pressure will do more for you gas mileage than all the fancy hybrids, alternative fuels, and other high-tech solutions (at least for now). While we’re at it – keep unnecessary items out of your car. Just taking that 20lb box of magazines you were going to recycle out of the trunk will improve your gas mileage more than nitrogen in the tires.
As for LiveScience – they get three thumbs down for their reporting of this topic. Trey Granger did not appear to spend even 5 minutes on Google seeing what is already published on the topic.