Ok so this and hydrokinetics can be somewhat complex so I'll explain the hydrokinetic thing a bit too to save you potential frustration. The most important rule to remember though is that the maximum speed and torque don't change, a hydrokinetic is still capped at .5MW of power regardless of fluid, different fluids just change how much blocks of it are required to achieve that max power. As for the stats the easiest way is an NEI dump, you'll want NEI Integration installed and then you under tools you can do a dump of fluid data, both viscosity and density matter with high density and low viscosity being preferred, water has 1000/1000 for reference. That said for the actual fluid here are the rough rules for height.
- Fluids of 900 temp or more will destroy the engine. Don't use them.
- Density has to be positive, no weird stuff with steam or anything that flow up.
- Both values are important, don't neglect either, particularly viscosity as even a small increase there can penalise you harshly.
- Technically if you're on other planets with Galacticraft it will scale with their gravity, of course I don't know of any planets with higher gravity so it will just require more height to reach max power.
- Technical formulas for height required for max torque/speed, you'll want the great one to achieve max power and round up. Ignore if you don't care about it and want to experiment.
- Height for torque is 200.575*sqrt(viscosity)/dens^(2/3)
- Height for speed is 1.975*sqrt(viscosity)
All of that means most fluids are actually worse than water either from stats or the fact it's vastly easier to get than anything of the same stats, it will vary from pack to pack but at least in my own fairly expanded infinity there is nothing that is better than water. It's really rather disappointing. Really the issue is that most fluids have the same density and viscosity, and that means that since density in torque scales up faster than lower viscosity scales it down you'll get a higher torque requirement and thus it will be worse. What you need are fluids with a lower viscosity than water and a higher density than their viscosity, to be precise you need a density of at least 5.6234 * visc^0.75 and a viscosity less than 1000 to be better than water, the only fluid I've ever found that meets that is jurassicraft cultivation fluid and that's only because it has a normal density of 1000 but a viscosity of 1 for some unknown reason, I've got no idea how to actually get it though for using.