I meant ethanol was not substituted for lead AFAIK - the lead was replaced with MTBE in practice, and then the story of ethanol blending has more to do with CO2 emissions reduction (or in the case of Australia, a conservative prime minister somehow getting away with a levy on milk to bail out his mate's ethanol plant and mandating 10% blending in fuel at the pumps).

Ethanol was the original anti knock agent, but afaik was actually replaced by tetraethyl lead originally.