In message , "Dave Plowman (News)"
writes
Trouble is, according to the classic car mags, the jury's out on whether
they actually work - unless they contain lead which most don't. An old
engine builds up a coating of lead and this can last for a long time after
the source is removed.

You can still buy leaded fuel though. The places that sell it are few
and far between but they do exist.
--
Clint Sharp