Leaded gasoline is getting scarce in the Boise area because of a federal law ordering gas suppliers to get the lead out by the end of this year.
Several major distributors stopped selling leaded gasoline late last year as supplies dwindled.
In 1990, Congress amended the Clean Air Act to ban sales of leaded gasoline for highway use by Dec. 31. The reason, the Environmental Protection Agency says, is health.
No estimate was available Tuesday from the Idaho Transportation Department on the number of vehicles in Idaho that require leaded regular gas.
But about 10 percent of gas sold in Idaho has been regular, estimated David Mabe, of the Idaho division of the Western Petroleum Marketers Association.