Not sure about synthetic but I will say that after using a better quality fluid, that cost just a little less than Kubota, I changed out to super UDT2 and results are amazing.
Was getting alot of whining noise from HST and relief valve always squealing. All gone after paying just a little more...
Looking for a kubota wholegoods catalog newer than 2013. Does anyone have experience on how to order from it? Looking for what was listed as ABXR8717 which is the front wheel/tire combination for my BX25.