Cars may use leaded or unleaded fuel. XGT class cars may use either leaded or unleaded gas. Leaded gasoline contaminates the oxygen sensors and catalytic converters. The low conical roof is covered with tiles but originally it was leaded. It is produced in the burning of typical leaded gasolines. Its pediment has dentils and a central, small, leaded oval window. Most homes built before 1960 contain heavily leaded paint. The fuel tank was and the car used leaded 95 octane petrol, getting . It is adapted to run on leaded gasoline as well as lead free gasoline. In all countries that have banned leaded gasoline, average blood lead levels have fallen sharply. Midgley's legacy has been scarred by the negative environmental impact of leaded gasoline and Freon. Studies have found a weak link between lead from leaded gasoline and crime rates. NASCAR eventually took steps to eliminate the need for leaded fuels. Its release into the environment as a product of leaded gasoline was highly controversial. The sale of leaded gasoline was outlawed in 2003.