It sounds like different areas may recomend different weight oils then. Our area said 50 weight but I would say do what the dealer says. As others have said the best thing to do is to change the oil frequently. If you think it doesn't look good then change it a little more often because I think no matter what the synthetic oil you use it will have similar issues. The oil is cheaper than changing the reaction arm bearing. In our hills we change the oil more often.

On another note we also run Gleaner combines and they have changed what oil to use in the transmissions and we have lost 4 transmissions using the oil they tell us to use and have no issues in our other combine running it with the oil they tell us not to use anymore. We got rid of the older one so will be running two with their recomended oil and will see what happens this summer in the hills. When they are paying the bill then I guess we have to do what they say.