Currently the only IGH which is oil lubricated from the factory is the Rohloff and it uses automotive type oil seals to keep the oil inside where it belongs. Recommended oil change interval is 3000 miles or yearly. All other IGHs are grease lubed using a very low viscosity grease as the grease needs to be able to flow in order to not be permanently forced out of high load areas of the hub gearing. SA lists 00 viscosity grease as suitable.