[Tigers] CASTROL SYNTEC 20W-50-a high-zinc formula specially engineered for classic engines.

[Thomas Witt]

Over on the Mopar site I frequent they are proponents of Rotella T for older
cars. It is diesel spec-ed. As I understand the Rotella T (maybe other
diesel spec-ed oils too) have added manganese and zinc. This helps with
scuff which is especially a benefit for non-roller cams. Unfortunately in
newer cars it also clogs the CAT, hence why it has been reduced (maybe
eliminated???) in most newer oils.

I just put a new cam in my 318 and used the Rotella T with a bottle of GM
EOS (engine oil supplement - which I have heard rumor isn't available
anymore either). A few hundred miles and the cam still has lobes so it is
doing something right.
Tom