Is that Penrite 20W-60 you are talking about, their mineral HPR 30 ?
If so, then that is a great oil. I have used it lots in both motorcycle and car. It's a high zinc and shear stable oil that was the go to high performance race oil back in the day. I always had very low oil consumption with HPR 30 compared to GTX 20W-50. It always ran smooth in my 6-cylinder '74 Holden. It has a high TBN too, for a longer drain interval.
I was once driving through the bush in that 70's Holden and I blew a radiator hose miles from anywhere. I managed to limp home with a sump of HPR 30 and a dry radiator. Fixed the car, no problems, it ran perfect for years afterwards.