Do Nitrogen-filled tires get better gas mileage than Air-filled tires?

Everyone agrees that to get the best gas mileage from a vehicle the tires need to be properly inflated to reduce rolling resistance and maintain optimum handling. Unfortunately, many drivers don’t check their tire pressure often enough and end up driving on under-inflated tires which reduces fuel economy.

As Gene Petersen of Consumer Reports notes, “fuel economy is related to the tire's rolling resistance, which is a function of load and inflation pressure. High load or low pressure causes a tire to have higher rolling resistance and, therefore, lower fuel economy. If the nitrogen retains the pressure better than air in a tire, fuel economy might benefit.”

Might? Why not a glowing endorsement by the folks at Consumer Reports for using Nitrogen in tires as a means of improving fuel economy? Perhaps it’s because “fuel economy” was not part of the Consumer Reports test which critics have found troubling and prompted the magazine to respond on their own blog to the hotly contested issue through a series of Q & A’s:

As Gene Petersen recounts, "for quick background on the nitrogen test: Consumer Reports wanted to find out if nitrogen is worth the price for passenger vehicles, so we evaluated pairs of 31 tire models of H- and V-speed rated, all-season tires used in our tread wear test from 2006. We filled one tire per model with air and the other with nitrogen. The test was quite simple: fill and set the inflation pressure at room temperature to 30 psi (pounds per square inch); set the tire outdoors for one year; and then recheck the inflation pressure at room temperature after a one year period.”

Click on chart to enlarge:

Here are a few of Gene Petersen's answers to some of the questions and comments posted on the Consumer Reports blog:

Q: I think we are missing some of the advantages here. First, the air loss mentioned above is 2.2 vs. 3.5 psi. That is a significant difference, even at this low inflation pressure. Also, nitrogen is an inert gas, and so will react with the rubber/chemical compounds much less, contributing to reduced wear. Another point is that nitrogen will not heat up like oxygen, so during extended highway driving you will reduce the over-inflation and wear/tear resulting from heat build-up.

A: Interesting points. Because nitrogen, in our case, is a processed gas (moisture and oil was filtered out by our nitrogen generator), you might expect better inflation control as the tire heats up under normal service vs. air with unregulated moisture, etc. And nitrogen has been shown by the government and industry to reduce tire aging.

Q: A flawed study and analysis. And sadly quiet on the advantages of using nitrogen in heavy trucks where 18 tires need to be maintained weekly to pressures of 100 psi.

A: The positive benefits of nitrogen in high(er) service pressure applications, such as used in large truck tires, has been documented in the industry. Our test centered on passenger tires, only. We are not discrediting the use of nitrogen, but it is not a substitute for regular inflation checks.

Not surprising then when the Get Nitrogen Institute, whose goal it is to provide consumers, over-the-road truckers, fleet managers and others information about the benefits of using nitrogen in tires, says:

“when it comes to tire inflation, nitrogen has many advantages over oxygen. With nitrogen tire inflation, improvements can be noted in a vehicle's handling, fuel efficiency and tire life through better tire pressure retention, improved fuel economy and cooler running tire temperatures.”

Another proponent of using Nitrogen is Bob Hazard, a technology consultant for the automotive industry, who has written an article “Nitrogen inflated tires: Pros and Cons” which says that (in addition to the commercial trucking industry):

NASCAR and the airlines have been using nitrogen in tires for quite some time,” and wonders “so why all the hype and controversy about the current trend to use nitrogen in passenger cars? Because it's new and because it's expensive (profitable). How hard can it be to sell when the FAA requires all commercial aircraft tires to be inflated with nitrogen? NASCAR teams use nitrogen because it allows them to more accurately predict tire pressure changes. Additionally, higher nitrogen levels eliminate the explosive properties of oxygen. So, with these endorsements, why can't you sell this to the consumer?”

Bob Hazard says he's "tried to come up with the cons and can't find any. There are no adverse affects from the use of nitrogen that I have found reported anywhere!"

It's not about the nitrogen. It's about reducing oxygen, water vapor and other gases. Proper tire pressure is a big deal, maintaining it with nitrogen you'll see these three primary benefits:

• Increased Fuel Efficiency
• Longer Tire Life
• Increased Safety

For More Information, please visit:
Consumer Reports “Tires - Nitrogen air loss study”:
http://blogs.consumerreports.org/cars/2007/10/tires-nitrogen-.html

Consumer Reports Blog Q & A:
http://blogs.consumerreports.org/cars/2007/10/nitrogen-tires-.html

Get Nitrogen Institute:
http://www.getnitrogen.org/
http://www.getnitrogen.org/environment/

Nitrogen inflated tires: Pros and Cons:
http://www.helium.com/items/772854-nitrogen-inflated-tires-pros-and-cons


Posted by Mark H. Baker