You have been downvoted, but you have a point. In the 1970s, you could buy both leaded and unleaded gas at service stations. New cars used unleaded gas, but o

You have been downvoted, but you have a point. In the 1970s, you could buy both leaded and unleaded gas at service stations. New cars used unleaded gas, but old ones "required" leaded for various reasons that turned out to be mostly wrong (http://www.stevelinden.com/unleaded-gas-vs-regular-gas-in-classic-cars http://www.stevelinden.com/unleaded-gas-vs-regular-gas-in-cl...). Unleaded was required to work with the catalytic converters that were newly required in cars. Regular leaded gas was cheaper. My neighbor had the catalytic converter in his car removed (it was illegal) so he could use the cheaper leaded gas. So there would be an effect in which old cars imply more lead.