I'm there right now. I have 10 gallons of Hy Tran Ultra waiting to be put into the tractor.
I asked the parts guy about the need to change the oil since it looked good and I seemed to remember one of the owners mentioning that all they did was change filters. We went to talk with the service guys. The consensus of opinion was that the additives that prevent corrosion and such tend to wear out, even though the oil looks fine. They also offered anecdotal experience about machines that come in with nice looking oil that hasn't been changed. The machines are not working quite right. A teardown shows sludge built up on interior parts. These are the guys who actually work on the tractors, not the ones selling parts. They know I can get the oil at someplace other than their store. Draw your own conclusion. I elected to buy the oil since it is cheaper than steel.