The good news is I just paid off my car loan. The bad news is I had to take out a loan to fill it up.

Burump-bump.

Hey, did you hear car thefts are down? Crime reports, however, have a new category: bikejackings.

But seriously, folks, the Smithsonian has announced plans to expand its dinosaur wing. Seems they need room for Hummers.

OK, I'm no Jay Leno, but the way I see it, we might as well try to make light of rising gas prices while they make light of our wallets.

If you're like me, you'd love to buy a hybrid, but the checkbook says you're going to have to hang onto that gas hog for a while longer.

So, to save on gas, you're driving a little slower these days and carrying extra cash for Tom's and other stations that give non-credit-card customers a price break.

You're also filling your tires with nitrogen.

A tale of two gases

"We don't bring it up with every customer," said the owner, Lewis Martin, "but when we're working on tires, we tell them."

For $5 apiece, Martin's will fill your tires with almost pure nitrogen, replacing the ordinary air that's 78 percent nitrogen and 21 percent oxygen.

Why do it? Well, there's some dispute about the benefit, but if proponents are correct, tires inflated with nitrogen stay fully inflated longer. And optimally inflated tires increase gas mileage and tire life.

When told the advantages, about four out of five customers pay the extra $20 for nitrogen in their tires, Martin said. Bert Donado of New Holland is one of them.

"My mom had it done in her car," said Donado, 35, a district manager for Rohm and Haas in Newark, Del.

"I was a little skeptical to get it done at first," he said. "But I put it in the tires of one of my cars, and it made a huge difference in the ride. And we even noticed the gas mileage was better."

Nicer ride. Improved mileage. Longer-wearing tires.

Donado is a convert. He now has nitrogen in the tires of his Lexus, Chevy Trailblazer, Audi and Nissan Maxima.

It's all about the bigger molecule, said Leon Hurst of Hurst Tire Service in East Earl, who invested about $10,000 in a nitrogen-replacement system last year and charges $3.50 per tire.

The nitrogen molecule is larger than the oxygen molecule and can't escape as easily through the tire wall.

And you didn't think size mattered.

Marginal improvements

Another advantage: Because water vapor is absent in tires filled with pure nitrogen, it's said wheels are less likely to rust.

So is there something to this, or is it too good to be true? I couldn't find a definitive answer.

Consumer Reports tested nitrogen against air in 31 tire models and found that over a year's time, air-filled tires averaged a loss of 3.5 pounds per square inch. Nitrogen-filled tires lost 2.2 psi.

The magazine's conclusion was that because all the tires lost pressure, consumers should check tire pressure routinely. Oh, yeah, clean your refrigerator coils every six months, too.

Hurst doesn't make big claims about improved mileage with nitrogen-filled tires. He's seen only a half-mile per gallon improvement in his GMC Yukon. He said higher mileage cars may improve from 30 mpg to 32 mpg, about a 6 percent improvement.

But a 6 percent savings on a $50 fill-up is $3, so it's easy to see how nitrogen-filled tires can pay for themselves in short order. And that's no joke. But this is:

Down on his luck, a man gets a flat tire. Getting out of his car, he walks into a bar.

He says, "Ouch!"

E-mail: jhawkes@lnpnews.com