"Grunff" wrote in message
...

A mid '70's engine might well last longer if Redex is used, even with
LRP.

If it's an iron cylinder head, unless it has hard seat inserts it needs
either leaded or LRP with an alternative additive, otherwise the head
will only last a few thousand miles.

It's usually aluminium heads that have the real problems. Lancia and Fiat
heads from the 70s/80s simply won't survive on modern fuels at all. Have
tried all the additives and none work that well.