And importantly in this context: The magic word is "piston-driven". Lots of aircraft you see look to a lay person like they don't have a jet engine, because there are propellers just like on a piston-engined plane. But a https://en.wikipedia.org/wiki/Turboprop is a very efficient jet engine that just happens to be driving a propeller and so they're running on JetA fuel which never had lead in it. (There are still lots of reasons not to exhaust that into the sky either, but at least it doesn't have lead in it)