Matthew, this topic has come up before with Kubota manuals. My '99 B2710 also said UDT, Super UDT, or 80W-90 gear oil. It came with UDT in it. Some think the heavier (thicker, higher viscosity, or however you want to describe it) 80W-90 provides better protection, while some think the thinner UDT or Super UDT can get into tight places that the thicker stuff might not. Personally, I think either one will get into everything that needs lubricating, but as to whether one is better than the other, I have no idea. I just decided that since it came with UDT, when I changed it I put UDT back in it.