I have a friend who owns a blue Fordson major, about a 1950 or so, manufactured in England. It is a diesel with a 3-speed transmission plus splitter. This may be considered a 6-speed forward with 2 reverse. When he first got the machine the hydraulics were working well. After a while, he started to lose lift power. He noticed the fluid was milky so he changed it with hydraulic fluid. Now it won't lift any weight at all. The three-point does, however, work without weight. Does anyone know if he is using the correct wt oil or should this be something like a 90 wt.