Lead in gas increased compression rations and allowed us to build higher horsepower engines. Lead is still used in avgas for this reason. Engine knock was a big problem at the time.
I wonder about lead levels in soil near gen aviation airports for this reason, and in the neighborhoods that sometimes get built on decommissioned runways.
I assume it's pretty inconsequential because if it weren't I'd hear real people talking about it (like with lead paint, and various forms of soil contamination) and as it stands I only hear fake internet comment section hand wringers hand wringing about it.
I'm sure you'd regard something like banning tail docking, ear cropping, or non medically necessary infant circumcision as similarly unimportant because only weird "chronically online" folks talk about it. "Just hand wringers". This is why the world is full of cruelty.
Ethanol has other downsides regarding corrosion and reacting with various organic and organic-ish (read: rubber) components. Those were bigger problems back then because everything was carbureted and they didn't have modern plastics.
> Oil companies and automobile manufacturers (especially General Motors, which owned the patent jointly filed by Kettering and Midgley) promoted the TEL additive as an inexpensive alternative superior to ethanol or ethanol-blended fuels, on which they could make very little profit.
Functionally, as others have commented, it is there to reduce knocking. But lead was used instead of ethanol (aka alcohol) because it was more profitable despite being poisonous.
It surely reduced it by a tiny amount compared to just straight octane, but ethanol reduced it by something like 10%. So using TEL instead of ethanol gave you about 10% higher gas mileage.
https://en.wikipedia.org/wiki/Energy_density#Chemical_reacti... says "Gasohol E10 (10% ethanol 90% gasoline by volume)" is 33.18MJ/liter, while "Petrol (Gasoline)" is 34.2MJ/liter. That's a 3% difference, which is much closer to your 1% or 2% than to the 10% I had believed. E85 is lower still in energy density.
All of this is assuming the engine has the same efficiency on both fuels, rather than, for example, using a much higher compression ratio on the ethanol.
At worst to get equivalent octane rating you lose about 4 percent in power density. In practice you won't notice due to the slightly more efficient burning of alcohol.
I'd always assumed it was some expensive-to-remove byproduct of manufacture or something, so they left it in to save costs despite the risks.
Why did this happen?