Well I met the other day an old mechanic with almost 90 years old, so..., you never knowsJim,
My dad is an ex Saab mechanic as well, he used to echo your comments about never seeing older mechanics so he found alternate employment and deterred me from that profession.
The question is if our pre-catalized cars pre88 do they have hardened valve seats from the factory? In other forums they said that our 900 engines has sodium filled valves and this protect the valves against knocking using unleaded benzin.The only cars that suffer from unleaded are those without hardened valve seats from the factory. Tetrathyl lead protected them; without it, they can be worn away by the valves. In those cases an additive will slow, but not stop, the wear. The only real solution is to install hardened valve seats.