My to30 hydraulics won't lift on their own. If I hold them up, they eventually build enough pressure to hold themselves up, but they can easily be pushed down. Soon as I shut the tractor off, they drop. I've replaced the control valve (which is where all my problems started). I couldn't find the correct mineral oil so I used STP Multitrac tractor fluid. Could this be my problem or am I dealing with bad seals on the piston? Getting a gauge tomorrow to test the pump pressure, but I really don't think that's the issue. Any help is greatly appreciated. TIA