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Events on Friday 9 December 1921 1
1921Tetraethyl lead stops the knockThe worst decision in the engine's historyThomas Midgley at General Motors finds that adding tetraethyl lead to petrol eliminates engine knock and allows higher compression ratios. It works beautifully. It also puts lead into the air of every city on earth for the next seventy years, with measurable effects on the intelligence of an entire generation. Midgley later invents CFCs.