Engine knock was one of the great early challenges faced by the motor industry. In an effort to outdo its rivals at Ford, General Motors (GM) began in the 1920s to look for a way to quiet the engines in its Cadillacs. One of its engineers, a man called Thomas Midgley, discovered that a drop of tetraethyl lead in gasoline would miraculously increase octane levels and stop all the pinging. And so began one of the most shameful stories of pollution in modern history—considerably more shameful than today’s carbon emissions, since while the science of global warming came after the adoption of
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