The 15-Minute Tip: Err on the Side of More Air

MarketWatch

Two simple steps can save you hundreds of dollars each year in gas costs

Instead of driving all over town looking for cheaper gas, consider this: A little more air in the right places can save you a lot of gas -- and money.

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This is what I mean: More air in your tires, and a clean air filter. And this money-saving tip won't take you even 15 minutes a month.

You can increase gas mileage up to 10% just by changing your air filter, according to the EPA's FuelEconomy.com site.

The air filter is a piece of thick corrugated paper with a rubber ring around it. And boy, does it get dirty. Like your furnace filter, but your house doesn't move. All that dust and smoke you drive through in your car? It becomes a dark grey or brown coating on your air filter. And that prevents your engine from getting enough clean air.

It's very easy to change the air filter on many cars. Most filters cost $5 to $15, according to the manager of a local AutoZone store. Two screws or a couple of clips, five minutes, and it's replaced.

Inflation due to under-inflation

The National Highway Traffic Safety Administration estimates one-in-four cars and one-in-three light trucks and SUVs has one or more tires under-inflated by 8 pounds per square inch (psi) or more.

The Carnegie Mellon University Sustainable Earth Club studied 81 random vehicles in a parking lot and found that 80 of the 81 had under-inflated tires. The average rate of under-inflation was 20% -- soft tires, indeed.

The EPA estimates that for every 1 psi of under-inflation, fuel economy drops by 0.4%. That's not much, but if the tires are under-inflated by 8 pounds, that's a 3.2% drop in fuel economy. About 1.2 billion gallons of fuel are wasted annually due to under-inflated tires, the NHTSA estimated in 2005.

Hundreds of dollars in savings

So, by changing your air filter and pumping up tires that were under-inflated by 8 pounds, you're likely to get a 13.2% improvement in your fuel mileage.

Take an average U.S. vehicle driven 12,000 miles at 20 miles per gallon. That's 600 gallons of fuel a year. At $3.60 per gallon, that's $2,160 a year.

Increase fuel economy 13.2%, to 22.64 miles per gallon: You use about 530 gallons, at a cost of $1,908 per year, for a savings of $252. Two cars would mean twice the savings. Drive more miles (and I know a lot of you do)? More savings. One or both of the vehicles is a heavy SUV? More savings.

Beyond the savings, properly inflated tires make the car handle better and make it much safer. In fact, that's what the NHTSA really cared about when it did the research.

Proper inflation also makes your tires last longer.

What to do

  • Change your car's air filter at least every six months. This is really easy for most cars, and it's basic cleanliness, just like changing your vacuum cleaner bag. Like those bags, keep a few extra filters on hand to make sure the nuisance factor doesn't get in the way.
  • Get a good tire gauge and use it. You don't have to spend a lot, but buying something better than the cheap pencil-style gauges is probably worth it. Check out the Accu-gage model on Amazon, or you can find many others at your local automotive store.
  • Watch for new technologies. Starting in 2008, all new cars are required to have automatic "TPMS" -- tire pressure monitoring systems -- to tell you if any tire deflates by 25% or more. These systems, already available on some luxury models, are nice, but they won't tell you if your pressure is down 20%. So, for fuel economy you still need to check.

Also, another cool new invention is just now making its way to market: An automatically self-inflating tire. A Czech company called Coda came up with a new technology, using the flex action of the tire to add air. It's making the auto show circuit now. I don't know how much it'll cost, but it may be a winner like radial tires were 50 years ago.

And, as much as it seems to make sense, don't over-inflate your tires. That brings new safety risks, and a Popular Mechanics study in 2006 suggested it did not lead to additional gas-mileage savings.

So, get the flab out of your tires and the filth out of your engine. Your car will feel better -- and so will you.

Jennifer Openshaw is the author of " The Millionaire Zone" and CEO of Openshaw's Family Financial Network. She hosts ABC Radio's Winning Advice and serves as an adviser to some of America's top corporations. You can reach her at jopenshaw@themillionairezone.com.

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