Dear Tom and Ray:

I'm writing for my brother, who never reads your column. He has a 2010 Toyota Prius with all the bells and whistles. He was told that to get the best gas mileage, he should buy low-rolling resistance tires. His dealer has never heard of them. What are they, and how do they increase gas mileage?

-- A loving sister who reads you guys a LOT, Margaret

RAY: Well, we're sure Mom always liked you better anyway, Margaret.

TOM: Your brother already has low-rolling resistance tires, Margaret. They come standard on every Prius.

RAY: I certainly can understand that he might not be aware of that. What I don't understand is why the dealer doesn't know about it -- unless he has a low-rolling attention span.

TOM: Here's the story on low-rolling resistance tires. Everybody's always looking for ways to increase gas mileage, right? One thing that decreases mileage is friction. As tires roll along the ground, they create what? Friction!

RAY: So the thinking goes, if tires could roll more easily, there would be less friction -- or rolling resistance -- slowing down the car, and the car's mileage would improve.

TOM: And lo and behold, this works! Tire manufacturers came up with new rubber compounds that allow cars to roll more freely while still maintaining a grip on the road. They're not designed for high-performance sports cars, but they function perfectly well for most people.

RAY: A person who buys a Prius is not going to drive it at high speeds around hairpin turns in the rain. Prius owners prioritize mileage over sports-car handling, so Toyota opted for a tire that maximizes what the buyers care most about.

TOM: Similarly, if you buy a Porsche, it's not going to come with no stinkin' low-rolling resistance tires. Because if you ask the average Goldman Sachs partner why he bought his 911 Targa 4S, the answer is not going to be "For the mileage."

RAY: But low-rolling resistance tires are available for non-hybrids now, too. And for people who don't need extraordinary handling qualities from their tires, they're a good way to boost your mileage by a few percent.