Every mile to the gallon counts nowadays.

That's why carmakers, looking for ways to meet consumer demands for higher-mileage vehicles, are returning to basics and using low rolling resistance tires to gain an additional mile or two per gallon.

Once reserved for hybrid vehicles, these energy-saving tires are finding their way onto more models such as the 2009 Ford Escape. Advances in tire compounds have helped tiremakers create more efficient choices for consumers looking for replacements down the road.

When Ford Motor Co. introduces its 2009 compact SUVs this summer, all of them will include low rolling resistance tires.

Using the 16-inch Michelin Latitude Tour low rolling resistance tires on its four-cylinder 2009 Escape boosted fuel economy by 1 mile per gallon, to 21 mpg in the city and 27 mpg on the highway.

When General Motors Corp. wanted to speed along the development of its hybrid SUVs, Scott Miller, the vehicle performance manager for full-size hybrid trucks, said the automaker used the Bridgestone low rolling resistance tires that GM had on its shelf, instead of starting from scratch with a new tire.

"Compared to our off-road tires, these deliver up to 2 miles per gallon better performance," Miller said. "Every bit helps."

Consumers, tired of putting $80 worth of gas into their tank twice a week, see fuel mileage as one of the most important factors in their next vehicle purchase.

"People react emotionally to the price of gas," said Eric Ibara, director of market valuation at Kelley Blue Book. "Sometimes people focus in on just one factor. They're trying to reduce their fuel cost."

How tires work

Michelin, along with other tire companies, continues its quest to reinvent the wheel, so to speak.

There are several factors needed to build a better tire, but first, you need to understand how regular tires work.

According to Dave Stafford, chief operating officer at Michelin Americas Research Co.: Tires, by their elastic nature, absorb energy in a process called flexing. When the engine spins the wheel, the tire flexes and turns that motion into heat. Mr. Science might explain it with this formula: (Tire power loss) = (Power input at wheel axis) -- (power output at the ground).

Rolling resistance is exaggerated when a tire is underinflated, which is why so many people tell you to check your tire pressure.

"Basically, every time it rotates it flexes," Stafford said. "That flexing causes those materials (in the tire) to absorb energy."

By using different materials, however, less energy is absorbed, and the tire uses more of the energy to move the car.

That's the gist: Reduce the resistance, and the tire becomes more efficient. A more efficient tire translates into better gas mileage.

The Green Seal, a nonprofit environmental organization, estimates that between 1.5 percent and 4.5 percent of all gasoline used by cars and trucks in the United States could be saved if all replacement tires were low resistance.

Tire cost is higher

So does that increase in mileage translate into real savings for consumers?

It certainly has an eco-marketing aspect. And Michelin estimates a set of its Latitude Tour HP tires can save you $300 or 68 gallons of gas during a lifetime of regular use. A set of Primacy MXV4 tires can save you 51 gallons of fuel or $200.

"There's the potential to recoup the price difference with energy saving tires," Stafford said.

Replacement tires vary in price by dealer. A search for low rolling resistance tires for the Ford Escape hybrid ranged in price from $150 to $260 per tire -- higher than a conventional one.

However, Miller adds that there is some give and take with low rolling resistance tires.

"You can get a lot of resistance out of the tire if you're willing to give up stopping distance," Miller said.

Stiffer tires don't absorb energy as well as conventional tires and can add a few feet to braking distance. "With big trucks, you can't trade off too much."

GM added 2 pounds per square inch to its low rolling resistance Bridgestones to help cut down additional resistance, but still give it a quiet ride and solid performance in wet conditions. There's more to the tires than merely adding higher pressure, warned Stafford; overinflating tires can be very dangerous.

Miller wouldn't advise taking the hybrids offroad with these tires.

Michelin plans to introduce a new series of Latitude tires that will include low rolling resistance models. They are the first set of tires to be Green X certified for the replacement market.

The company sells its Energy Saver tires in Europe. Since the company began selling energy saving tires 15 years ago, it has sold 570 million and estimates that it has helped save 2.38 billion gallons of fuel.

Saving a mile a gallon may not translate into much with any given tank, but as gas prices continue to climb, it's easy to see why every mile counts.

Scott Burgess is the auto critic for The Detroit News. You can reach him at (313) 223-3217 or sburgess@detnews.com...

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