Tetraethyl lead started to be added to petrol in 1921 when three engineers at General Motors discovered that it greatly improved engine performance and reduced "knocking"—uneven burning of the ...

Lead was added to fuel for most of the 20th century. (Joe Mabel/Wikimedia commons/CC-BY-SA 3.0) Tetraethyl lead started to be added to petrol in 1921 when three engineers at General Motors discovered ...