I have an older Woods 5120 Mow n Machine ser # 337732. I want to change the oil in my hydro units. I can't seem to find the perfect answer to my question of what oil should be used. I don't have a local dealer in my area. The mower is going to be used for my yard only, about one acre. If I can use a standard off the shelve oil I will do an oil change each spring. I'm not sure what to call the hydro unit. I see gemini and eaton mentioned. Woods tells me to use 71178 hydrostatic oil. Any help?