This is the first new piece of equipment I've had the pleasure of owning so its my introduction to the mysteries of the Kubota 50 hour service. I've read the owners manual, perused the WSM, and read many threads in this forum about the 50 hour service for other equipment. For the SSV75 the requirement is engine oil/filter and hydraulic filter. If I choose not to replace the hydraulic fluid how much do I need to drain to remove the filter and avoid bathing in hydraulic fluid?