I've got a 06 model Mini Z, 19hp Kawasaki 42in cut. My time is coming near on the hydraulic fluid change and i'd like to do it myself. I have two questions: My manual recommends 20w50 oil for the hydro drive. If I choose to use a synthetic oil, do I use 20w50 synthetic or Mobil I 15w50 synthetic as indicated by a couple of archived threads on here? To drain and purge the system of old fluid what is the procedure? My manual mentions it needs to be done but that's all. Is the drain on the bottom of the reservoir, and with the filter removed and mower off the ground should the tires be spun to purge any remaining fluid? Finally, what is the capacity on new fluid. Thanks in advance.