I have 2 X-Ones that need their first fluid changes. These are my first zero turns to service. I have looked through the GSM and I see the it recommends "SAE 20/50 SL/SM" motor oil for the hydraulic system. Do you have any preference on what brand oil goes into the hyd system? I have found only 4 types readily available here. Mobil 1, Castrol Syn Blend, Castrol GTX, and Honda. All meet the "SL/SM" standard except the Mobil 1, its stamped SJ i believe. Is there some difference in the oil that would make the Castrol a better choice for this application over Mobil 1 fully synthetic? Thanks in advance.