ODESSA, Fla. — When you're 13, like Savannah Walters, and the world is your oyster, you can do more than try to become an Olympic equestrian — you can also try to change the world.
"The future is what I'm worried about," says Walters, "the future of all wildlife, all people and our planet."
Walters was shocked to learn how careless American motorists are: Of 300 million tires produced here annually, the Rubber Manufacturers Association says an estimated 85 percent are driven with too little air.
"We waste 4 million gallons of gas a day, every day," says the Alaska Wilderness League’s Lenny Kohm, "just because our tires are underinflated."
So, five years ago, Savannah Walters launched a campaign. Now, with friends in her Florida neighborhood, she goes car to car — not just measuring tire pressures, but dispensing advice to drivers.
Walters does more than patrol the neighborhood. She also maintains a Web site, which has prompted "pump ’em up" campaigns in at least 10 other states. She's also lobbied in the halls of Congress — recently, on the Capitol steps, telling a cheering crowd at a rally, "The least we can do is, pump ’em up!"
All this has earned praise from her fellow 7th-graders, like 12-year-old classmate Kirsten Dewey, who says, "It's inspired me, because I realize every person can make a difference."
And, says Dan Zielinski of the Rubber Manufacturers Association, it’s a difference that can benefit drivers of all ages.
"Properly inflated tires, according to the federal government, can save you up to 3 percent on your fuel bill each month," says Zielinski.
That, says Walters, is good for the pocketbook and good for America.
"I have a tool that costs about 99 cents that will save us a million gallons of gas a day, starting today," Walters says. "[It's] a tire gauge!"
She is, indeed, gauging the difference — and making one.
© 2013 NBCNews.com Reprints