I've been given an elderly (40-50 years) cultivator - 4 stroke Briggs
and Stratton single cylinder engine. Seems to be all OK and the
engine runs fine. However I believe I should be adding something to
the petrol to make it equivalent to that containing lead.

A local agricultural machinery company said this wasn't necessary, but
a decoke would be advisable.

What's the collective's opinion please ?

Thanks

Rob