I'm not a master mechanic Bob but I just use the oil the manual recommends. I don't think it matters if you use 30 wt oil or EP oil as long as it is brass compatible. Since my tractor has so much time on it I have considered using a thicker oil or an EP oil when I make the next oil change for the drive train.
I don't think there is a real “correct” oil as long as it's a good oil and at least 30 wt. or thicker. I wouldn't use the hyd. tranny oil for sure.