The dealer told me to just use universal hydraulic oil. I told him I had some AW 32 that I used in my Yanmar and he said that any of it would work in our climate. It says it meets the JD-20C and Kubota SUDT spec so I figured it would work in a gear drive. No problems so far but I only put in about a gallon. Not near 200 hours yet so I have time to research it prior to dumping the 15 or so gallons out. I think I will put that same oil in my Kubota when I change it out which wont be too much longer. I changed hydraulic filters on the HST transmission on the Kubota and it opens the reservoir to drain and even as quick as I could screw on the new one, I lost about 2 gallons so I put back the SUDT for it this time. At least with the LS, you only loose what is in the filter and a little in the line, but it will continue to leak a bit until you get the new one on. I had a disc or bushhog or box blade (cant remember which) but had something on the 3 PH so I was sliding around under the tractor. Best to take anything off the back and make it easier to get to. Have big container slide under the syrup bucket filter and as soon as it is off pop the other one on and you wont loose much oil at all, just basically what the filter holds.