Hydraulic Fluid Choices

[Cougsfan]

Maybe I am wrong but it seems to me like people are overthinking this. There are a multitude of transmission fluids that have worked just fine over the decades. There are improper fluids but many proper ones. Nothing has changed in transmission and hydraulic systems that drastically changed fluid requirements in the recent past. There is a wide choice of acceptable fluids and none have a significant advantage. It's sort of like debating which engine oil to use; the time to show your brand prejudice.

Unlike in an engine where synthetics are significantly superior, I think synthetics don't show that same significant advantage in a hydraulic system. They will work just fine and may be theoretically better, but aren't so much better that you will notice a difference.

 

[ericm979]

I think the one situation where synthetics may be better is lower viscosity at low temps while keeping good viscosity at working temps. It doesn't matter for me much as it rarely gets much below freezing here but in other places it would.

The semi-synthetic I put in last time seemed to make the HST quieter at startup. I might have been imagining it.

 

[YanmarFever]

Our 10' bush hog mower head does not get as hot when we run pure synthetic gear oil in it.

 

[LouNY]

I'm not sure on the small tractors but on the larger ones as the hydraulic pressures and flow rates have gone up, so have the hydraulic fluid specifications.
Most of them now need at least a para-synthetic or even a full synthetic to meet specs.