Now about leaded fuel. Back before say, 1970ish a lot of gas had an octane rating of between 40-70[1]. Refining oil was still an emerging technology. That being the case it seems like one of the by products of Natural Gas Liquids(called Natural Gasoline) was being used as pump gas. Lets pretend that you built a time machine and took your brand new 2022 camry with you to have a laugh that a consumer commuter car would be a super car back in the 1940s. If you managed to find fuel that was unleaded you would likely do irreversible engine damage on the first tank. If you filled with leaded, your catalytic converter would foul and then you would need to remove it to run leaded fuel. Lead was an additive because it prevents detonation in sub-optimal gas. After lead was outlawed they started boosting octane to do the same function. Fuel sucked, and it wasnt until lead was outlawed that refining higher quality fuels on a large scale became possible. I see the clean air act as a great example of successful regulation.
[1]https://www.energy.gov/eere/vehicles/fact-940-august-29-2016...