My hydraulic fluid is milky with water in my Bobcat 773. How do I drain the milky fluid from the entire system before installing new filter and fluid? No Bobcat dealer near so can I use tractor hydraulic fluid? Can I use 10-30w motor oil instead of hydraulic fluid? Before changing the fluid, should I empty the filter and run it to get more sludge in the filter, then empty it again and do this several time to get as much sludge out with the old filter before installing a new filter and fluid?