which oil to use
Some of the synthetic Amsoil formulations have some of the highest, useful concentrations of zinc and phosphorous. I've been using the stuff for many years.
As mentioned, the hardening seals is a fairytale.
Here is a link to an Amsoil Technical Bulletin on the products and the issues.
https://www.amsoil.com/dealer/techservicesbulletin/MotorOil/TSB MO-2007-08-08 Flat Tappet.pdf
Amsoil source & info site:
www.thelubepage.com
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