Was BS from the start in order to exploit people with absolutely no understanding of ordinary chemistry.
Lead is insoluable in petrol, always was always will be.
In fact back before lead became the devils metal and just looking at some will cause your balls to fall off petrol tanks for cars were made from TernPlate which is similar to tin plate but the coating is pure lead .
This is why old car fuel tanks don't rust through where as more modern tanks rust through while you are watching .