That depends on how you roll. The better a tire retains its shape, the less energy it uses to turn. Fuel-efficient tires offer the lowest such rolling resistance, as it's called, and they usually come fitted on new cars. Replace them with an ordinary set and your mileage might drop, a cost not included on your new tires' price tag.
That's changing. Proposed California regulations would require manufacturers to report rolling resistance for all tires sold in the state, and the California Energy Commission plans to release a consumer shopping guide ranking tires by 2011. The federal government is considering a label of its own, so in coming years these babies should be burning rubber.
That, however, is literally what some models do, so shop carefully. According to the Transportation Research Board, low resistance could come at the price of reduced traction and durability. You can bet your brake pads that labs are at work designing tougher, safer, fuel-sparing radials, and Washington’s labels would rank all three crucial factors. To learn to size up a tire’s specs, search AAA.com  for "how to choose tires." Right now, the sole group testing and rating rolling resistance is the subscription-only consumerreports.org .
AAA members get special savings at Big O Tires. For more information, visit AAA.com/discounts .
This article was first published in September 2009. Some facts may have aged gracelessly. Please call ahead to verify information.