Can anyone offer any ideas as to what to do? I have a Gravely Promaster 148Z with hydraulic lift. I recently changed the hydraulic fluid and filter, and have been having problems since. Yes, I used the correct oil - 15w-50 synthetic. I bled the lines, yet I still get a sluggish lift. Lately, I can't get it past 4 in. height. I blew out all the lines. The lift lever doesn't stick. It drives just fine, so I figure the pumps are good. Also, the fluid hasn't gone down at all. I changed out about 2 months ago. There is no info on this problem that I can find in the forums, or the net. Thanks for your help.