What is a leaded gasoline?

A leaded gasoline is one that has a lead-containing compound in it.

For many years the number one anti-knock agent was tetra-ethyl-lead. After epidemiological research showed that the lead dust coming from car exhausts was a major cause of lowered intelligence in children the use of this chemical was quickly phased out. The use of any lead compound in gasoline has been a Federal offence for some years now. Leaded gasoline is still available as a high octane aviation gasoliine.