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9th December 1921: Lead identified as a fuel additive for automobiles

2,419 views · Published 9 December 2018 · 2:48 · Indexed 13 October 2026

Channel: HistoryPod · 2018 · Education

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Engine knock, sometimes referred to as ‘pinging’, is caused by the improper timing of fuel combustion in an engine’s cycle. By occurring too early, the explosive ignition causes a shock-wave that can cause serious damage to the engine cylinder.

Thomas Midgeley Jr. was a mechanical engineer at the US automobile manufacturer General Motors, where he was tasked with finding a way to prevent engine knock. Although he had already found that mixing gasoline with ethanol would reduce knock by raising the octane level of the fuel, it was a process that was impossible to patent and thus make any significant profit from.

Midgeley continued his search for a suitable additive and on 9 December 1921, after working through thousands of chemicals, he finally identified tetraethyl lead. Ignoring the dangers that this neurotoxin presented, leaded gasoline soon became a standard feature on forecourts across the world while the additive itself became known as TEL under the brand name Ethyl. 

A few months after his discovery, Midgeley had to take time away from the laboratory due to lead poisoning. Some of his colleagues were not as lucky. Within a year ten workers at the lead plant had died, while dozens more experienced neurological symptoms including tremors, hallucinations and fits. Despite these evident dangers, leaded gasoline continued to be the standard fuel for automobiles until it was ordered to be phased out in the 1970s.

Midgeley himself later went on to develop the first CFCs, making him the creator of two products that have caused serious long-lasting damage to both human health and the environment.

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