I don't dispute what you say, however you have to look at how Case owners use oil.
The Onan and Kohler engine manuals are very clear on this issue. If the temps are above freezing, then you use 30 weight oil and you change it every 25 hours.
The hydraulic system requires 20W40, 20W50, 30 or 15W40 in order to deliver maximum power to the rear wheels. That oil is supposed to be changed once per year or every 500 hours, whichever comes first. In truth, there is no real need to go with a more expensive oil than Shell's Rotella costs. There is no way for anyone to determine whether the Shaeffer is superior to Shell or not. I have yet to hear a report from an owner stating that their engine had major amounts of sludge inside of it. If you change the oil when you should, then you won't have oil-related problems.
When you consider how little oil is used in these tractors, all of this discussion about this oil being better than that oil is truly pointless and often leads to threads with flames emanating from it. If Schaeffer works for you, then by all means..... continue to use it. I am not going to try to talk you out of it because there is no valid reason to do so. On the flip side, we have a lot of member/owners who are very pleased with Rotella or some other brand. Oil is a personal choice and everyone should respect that, while others should stop proselytizing.