I've owned this tractor two years. Used it last year and it worked fine. This year, hydraulics WILL NOT LOWER. It lifts OK. I checkrf the fluid (oil). It was dry! I put in 2 gallons of 85-90 oil. Still won't lower. Does anyone know the correct oil capacity for this unit? How much more than the 2 gals I've already added? Any other thoughts on this hydraulic issue?