I have a Hitachi ZX30u-2 with 9000 hours on it. I am looking to replace the hydraulic fluid and have seen few different results with using type of hydraulic fluid where some say use zinc free and others say use normal hydraulic fluid. I am having a few issues with the machine not having enough power or feels slower than normal hydraulic wise. I have replaced the drive motor on one side and redone the swing motor/centre joint seals together with numerous different leaks in the hydraulic system. I have had issues with throttle failure on rare occasions and it goes away with restarting the engine. I am currently trying to fix as much as possible but getting to a point where I need bit of assistance please.
I always go with whatever the manual called for. While I realize that there have been leaps and bounds in lubricants, for me, I always feel safer going either way what the systems were designed for, I will admit, the snake oil salesman, always get me, on a lot of stuff. One time on an HD tranny, put some additive in it and it ruined the clutch plates, right quick.