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according to the article > Oil companies and automobile manufacturers (especially General Motors, which owned the patent jointly filed by Kettering and Midgley

according to the article > 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.

kragen 1y ago
It also gave better gas mileage.
- marcosdumay 1y ago
  It allowed people to use engines with better gas mileage, what is a different thing. Just adding the lead addictive to gasoline reduced your gas mileage. But it made better engines work.
  - kragen 1y ago
    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.
    - consp 1y ago
      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.
      - kragen 1y ago
        I don't think that is correct.
    - marcosdumay 1y ago
      If you are comparing it to pure ethanol, yeah, that's the ballpark. Leaded gas compared to ethanol mixed gas with equivalent octane numbers should have something around 1% or 2% difference.
      - kragen 1y ago
        https://en.wikipedia.org/wiki/Energy_density#Chemical_reactions_(oxidation) 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.

kragen 1y ago

It also gave better gas mileage.

marcosdumay 1y ago
It allowed people to use engines with better gas mileage, what is a different thing. Just adding the lead addictive to gasoline reduced your gas mileage. But it made better engines work.
- kragen 1y ago
  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.
  - consp 1y ago
    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.
    - kragen 1y ago
      I don't think that is correct.
  - marcosdumay 1y ago
    If you are comparing it to pure ethanol, yeah, that's the ballpark. Leaded gas compared to ethanol mixed gas with equivalent octane numbers should have something around 1% or 2% difference.
    - kragen 1y ago
      https://en.wikipedia.org/wiki/Energy_density#Chemical_reactions_(oxidation) 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.