I heard some people are using rotella oil in their cars. What is the advantage and what weight are they using.
Antique Engine Rebuilding near me says no Zinc. Zinc only need for steel camshafts, Model A has cast iron camshaft. Furthermore, a majority of people use no zinc and everything is fine.
Model A has a steel camshaft!
Model A has a steel camshaft!
And therefore Zinc (ZSSC) is required but did the oils of the 1920s have zinc added?.
This is a subject much debated, varying opinions, no consensus. You can use the Search function here, read all the info, then it is up to you. Just remember just about any oil today is much better than oil in the 30s. Change the oil often if a stock setup, and when the oil starts looking dirty. My opinion is keeping the oil in your A fresh/clean is much more important than the type/brand used
I agree, if so many people are using so many different grades with positive results then I think what you use is less important than keep the level up and keeping it clean. No comparisons to today's oils to oil available 90 years ago