Oil choice is probably not much of an issue in a car that isn't driven much.
I use either Rotella 30W or Quaker State 30W in both my Kaisers, 2 Wheelhorse tractors and a '52 Ford 8N tractor.
I have put 15,000 miles on the Kaisers in the past 6 years. And one of those went non-stop 9 days to CA.
One Wheelhorse is 33 years old and the other 25.
I have used the 8N, running at full throttle with a 6' mower deck on back, to cut 5 acres for the past 27 years.
With these experiences, I think that I have made the correct choice in oils!