VR1. Mineral or full synthetic

What you may not know: some oils, mainly those for production cars, are friction modified. In simple terms, the oil thins out when hot to get better mileage. This came about in the late 70s/early 80s with the oil shortage, & EPA forcing better mileage.
I found out the hard way; my engine suddenly lost about 10 psi at idle. The oil had had the FM treatment. In this country they sell oil that is NOT FMed & it is clearly printed on the label. Not sure in the US, but maybe 'Performance' oils are exempt from FM, which might explain the low idle pressure in post #41.

As for what Chr recommended in the 70s......much has changed.