Cannot Compress Hydraulic oil. Doesn't matter how much pressure you apply to it. Cannot fit 100 ml 3 of oil into a 99 ml 3 Container.
This is venturing into the realm of Fluid Mechanics. Viscosity = x = 1E/2 e 3 And all that.
And the answer is ... No ...What I am wondering though is say one type of fluid able to handle a greater load in the same cylinder?
Using thinner oil would probably blow the seals out quicker thou.
Brake fluid DOT 5. Wouldn't even reach the celing pressure. Just blow past everything.
ATF and HYD oil have similar Viscosity's. The difference would be too slight to notice BUT, The pump (depending on what Type/Make) would have to work a little harder to reach Full pressure = Slightly Less component life. This is true across the whole system.