It's hard to know what's myth and what's fact. I remember everyone saying Castrol was no good. In the next breath they said Shell was no good as well.
We always used Mobil but only because that was the local fuel distributor. One Tractor we had did 8000 hours and we only rebuilt it because the liners got cavitation holes in them. Oil changed every 100 hours with Mobil 30 grade. Now Mobil has disappeared and I mostly use Gulf Western because the local heavy vehicle business uses and supplies it.
My John Deere Tractor is still under warranty and is using JD oil.
Westrac maintained all the gear at Cadia when I was there. They didn't seem to have too many engine issues. Very regular PM on the gear and the operators were kept in line. I did see one block out of a 793 dump truck (78 litre cat V12) that had hand grenaded from an over rev though.
It's interesting to read what people have found when they have pulled engines down though. Clearly not all oils are equal, just like filters and fuel.