I haven't spent much time on here lately ,sorry it's been awhile since my last post , as novaman explained it , your seals on the piston are leaking a liitle, not enough to make the cylinder not lift but enough to leak to other side and when you let it down it pushes it out the vent , a single acting cylinder shouldn't have any oil on the top side . If you are able to take it apart yourself your should just need to get new rings at a hydralic shop and put them on , make sure to put oil on the new rings so you don't damage them when you put it back together. If you need to take it to a shop to have it done ,depending what it costs it maybe cheaper to get new cylinder from a place like tractor supply , I looked it up and they have a 3x8 for $109.95 and a 2.5x8 for $99.99 , these would double acting and you would need to put a vent in the top . Repair shops can get $60-$70/hr. and it don't take much to use up 1 hour or more on a seemingly simple job. If you can do it yourself it shouldn't cost too much.
