Unfortunately, everyone seems to have a different idea and no one seems to know for sure. Search on Super UDT in the current board and in the archives. Lots of interesting reading. The most interesting was a post where someone quoted Kubota as saying the Super UDT was synthetic, but that has not been reported that way before. I would pay the difference if it really was synthetic, but no way to tell for sure. Since my tractor is a gear tractor, it makes less difference than if I had a hydrostatic transmission. It also seldom get cold enough in Texas to justify the Super UDT. I don't know why something that should be as straight forward as this is such a mystery! /w3tcompact/icons/smile.gif