I just bought a Komatsu PC27R. I used it a little and all works fine, I changed all the fluids and filters. When changing hydraulic fluid, I used Universal Tractor Hydraulic Fluid from TSC. The premium stuff. Now after using it for around 10 hours the pump is whining when under a load and the bucket cylinder has started to leak a bit. I looked online and found that this machine is supposed to use 10W motor oil in the hydraulics. Anyone with any experience with this change in oil causing a problem?
I can't see it being a problem.
My old Bobcat blew a hose. Guys replaced the hose and refilled it with universal tractor fluid. It started screaming when started. Had to change the fluid. Do not see how that could be related to your cylinder leaking.
Starting to worry it may be the pump. It only has 1500 hrs on it though.