It would have to be proven that use of an "alternative" brand of oil caused the failure. It is a violation of the Magnuson-Moss Warranty Act, passed in 1975, to require that you used the company branded products exclusively to maintain the warranty. Since there is no other alternative to Kubota's Super UDT and Super UDT2, then using anything other than the Kubota product could jeopardize the warranty on the hydrostatic drive unit, but as far as engine oil, as long as the oil that you use has the same "symbol's on the container as the Kubota branded oil, you are OK.
I remember when I had my Mercedes, Mercedes Benz would publish a list of approved oils and lubricants every year. That list was quite long and extensive with so many brands that you had lots of choices of oil brands.
I get that. But I also get-that “You can beat the Rap.... but you can’t beat the RIDE!”
When I was working law enforcement my supervisory/partner kept telling me that as he was referring to the times he demonstrated how to “get back” at an uncooperative subject. We had pulled-over a guy with a missing license plate ...(it had clearly just fallen off as the front plate was still on the car, his registration was in-order, and the inspection and insurance was current.).... but he driver decided this was the time he was going to give my partner a bad-time and stated, “Why don’t you go catch a criminal instead of stopping regular citizens?” But he said it in a foul-languaged-version).
My partner wrote him a citation and when we got back into the car I told him “You know he’s gonna beat that in court, don’t you?”
”yeah”, partner replied, “... he’ll beat the Rap.... but he ain’t gonna beat the ride!”
My partner deliberately missed the court-date and the judge “continued” the case (meaning the subject would have to return a second-time to court).... Partner missed next court also. Judge dismissed the case... but the subject missed two days of his life fighting what COULD have been a simple matter of being courteous during the original traffic stop.
You can use whatever Fluid you want in your tractor. It’s your tractor.
But it’s Kubotas’ warranty and you might have to document if Rotella or whatever actually meets the specifications called-for in the Owner’s Manual. When was the last time you had White Laboratories or Blackstone Labs run a compatibility test and what did that cost you?
I’ll bet Kubota fluid is cheaper.