Antiknock agent
 Gasoline is a fuel mixture. High compression internal combustion engines place gasoline under great pressure. A.H. Gibson and Harry Ricardo in England and Thomas Midgley, Jr. and Thomas Boyd in the United States led early research into this effect. They discovery that lead additives ended or reduced knocking. So, most gasoline brands started adding lead in the 1920s. The lead antiknocking agents allowed the sale of even more powerful, higher compression car engines.