I have a soon to be 1 year old Kubota Grand L 3240HSTC with only 20 hours of light duty use on it. I am going to change engine oil and filter (even though oil still looks new) and am asking if hydraulic and HST filters should be changed also. I know manual advises to do it at 50 hours, but it has been almost a year and probably 1/2 those hours were from moving snow last winter. Temperature ranges from -20 to 100+ during the year and I am thinking about the condensation being in there. I don't think I would change those fluids, just the filters. Dealer wants $120.00 for the 2 filters. What would you do? Also I am thinking about using Rotella diesel oil when I change it. Is there any warranty concerns doing this?