Hi all----I just registered as a new member, and so I want to pose this question. While I am not a "Mr. Goodwrench", I am not totally clueless either. I recently purchased a Scag Liberty Z 48", and to this point am really happy with it. The question is whether or not it is advisable, after less that 10 hours on the machine, to drain the hydraulic oil and refill with a synthetic 20W50, such as Amsoil. The operators manual recommends this be done at 120 hours. Amsoil claims their product is specially formulated for zero turn mower hydrostatic transmissions vs 20W50 motor oil. Am I correct to feel that you can't change the oil too much or too soon? Also, I do plan to drain the KAWA engine at the early stage of 8 hours and fill with Mobil 1 20W50 along with using the Mobil 1 M1 102A filter. I contacted the tech dept at Mobil 1 and they said that this filter will work, though it has a slightly larger capacity.