I also find it amusing that we still call that petrol “unleaded,” as if to imply that the natural state of petrol is leaded and some company has kindly removed the lead from it to make it safer, rather than never adding it.
I don't know, "unleaded" sounds kind of like "unleavened", where leavening was never added in the first place. I think "deleaded" might be closer to "lead removed", if it were a word.
