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Originally Posted by Detroit Free Press
BY MARK PHELAN
FREE PRESS COLUMNIST
August 6, 2006
Filling his tires with nitrogen may help Mark Martin race his Ford Fusion at NASCAR's Brickyard 400 in Indianapolis today. But despite the claims of some retailers, it's not likely to do you much good when you drive to work tomorrow.
A street car's "tire doesn't care if it's filled with air or nitrogen," said Richard Gratz, General Motors' engineering group manager for tire and wheel systems.
That's a far cry from the breathless promises some retailers make: "You could save up to $150 a year on gas" using nitrogen, according to one ad. Another pledges tires "will last longer, and you'll get better gas mileage."
With gasoline prices at record highs, that gets your attention. Retailers across the country -- from the neighborhood tire shop to warehouse giant Costco -- are offering nitrogen fill-ups to improve gas mileage and prolong tire life.
Some fill every tire they sell with nitrogen for free. Others charge $2 to $5 to fill any tire with the gas, which is the most plentiful element in Earth's atmosphere.
"It won't hurt, but we feel that the claims are greatly exaggerated," said Gratz, who oversees testing and development of the millions of tires GM buys every year.
But if nitrogen is good enough for the 200-m.p.h. race cars at the Indianapolis 500, it'll do wonders for your Dodge Voyager minivan, right?
Not necessarily, says Terry Hendricks, a chassis engineer for Roush Performance Products, the Livonia-based engineering house that helped develop the 500-horsepower Ford Shelby GT 500. Nitrogen makes a difference for highly stressed racing tires, but it's not likely to make a difference on even high-performance street cars, he said.
Racers use nitrogen because it leaks out of tires more slowly than regular air, said Belle Tire training manager Gary Schlachter. It also contracts and expands less than air as the temperature changes. Belle Tire puts nitrogen in every new tire it sells and will fill other tires for $4 each.
"Nitrogen maintains more consistent tire pressure over time, and this can improve fuel economy and tire life" in normal driving, Schlachter said.
Matt Mio, associate professor of chemistry at the University of Detroit Mercy, said nitrogen's chemical behavior doesn't support those claims.
The retailers' claims "are more marketing than real effect," Mio said.
Costco, which markets nitrogen fill-ups in the tires it sells, did not return phone calls.
"We have seen no data that there's any difference in fuel economy," GM's Gratz said. "Correct tire pressure is the key. Drivers should check it every month. We don't want people getting a false impression that they don't need to check their tires as frequently."
Goodyear Tire and Rubber Co., the largest U.S.-based tire maker, declined to comment on whether nitrogen improves fuel economy or tire life. But Goodyear is focusing on its Free Air campaign, which encourages drivers to keep their tires at the manufacturer's recommended pressure.
Everybody involved seems to agree that works.
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