estutjaweh said:
The reason that Rohloff use oil is simply that it is a "returning" lubricant. Grease is not....
Although this is basically true, keep in mind that most IGH are grease hubs.
The rule of thumb is: grease for bearings (ball or roller) and oil for bushings. The rolling action of bearings will draw grease in. Gear teeth can work with both, but under high loads, the teeth tend to squeegee the grease off the wear surface.
With gear boxes, oil baths tend to have less drag than grease, and is one of the reasons Rohloff uses it. You loose a bit on the seals though.
Rohloff uses roller and ball bearing throughout the gears, whereas most of the other IGH hubs use bushings (which also use grease!).
As I said before, the the main issue with grease in a Rohloff is mucking up the clutch mechs, which can leave your hub freewheeling when it gets cold. There is also the warranty issue, I've been told that there are carbon parts in the hub that can react to different oils, and thus their insistence on using their special oils. Because it is a high $ item, and they have good CS, I won't admit to putting anything other than the sanctioned fluids in my hubs...
As for running out of oil, you should not be overly concerned. The idea is to wet all the wear surfaces with oil, and whatever remains clinging to the metal surfaces is all you need (for the next ~2 years). Even after a lot of weeping, there is still a fair bit of oil inside. I understand that you really only need about 15ml of the 30ml that they tell you to put in during an oil change.
I usually put in ~20ml after a rinse, and let it weep for a month, after which it's fine. I do have to clean the disc rotor until it stops weeping - which is a pain.
