Comments by "Stephen Villano" (@spvillano) on "Veritasium" channel.

@ls6jay true, though it's part lubrication, partly cushioning the valves when they closed. Modern components can withstand those stresses, old engines either needed a change of valves and seats or have leaded fuel. But, confounding the story is another source of lead that remains a problem today, lead paint. Ironically, there's still another source and one that's two feet away from me, lead solder for electronic circuits. Now, modern solders use greater amounts of silver and tin, which then introduces tin whiskers into the mess...
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My mother was a seamstress and knew sewing machines inside and out. I took that and well, always have been good with mechanical things and figured out the finer details, such as gear timing and finding timing marks to sync up the shuttle and needle. Came in handy when removing a shuttle, as someone forced the cloth through and bent the needle, burring the shuttle and catching and not releasing the thread. And figuring out bobbin tension problems.
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@thetaqjr nail nearly hit on the head. Per capita is part of the equation, so is total harm vs gain. Which is why we don't have leaded gas or paint today.
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Drop something in orbit, it'll stay in orbit. Nothing decelerated it so that it'll stop falling around the earth.
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