Andrew R Stewart 

I have dripped medium viscosity oil into many IGH axles/hubs via the indicator rod hole. Any factory grease isn't a life time never needing attention product and grease will dry out over time. having said that adding a thinner and fluid lube can cause more weeping/seeping out of the lube from the hub (and this is why an oil only hub like the older SA AWs show such grimy spokes over time, the weeping out oil get's pulled to the most outer part of the rotating wheel). If one bothers to wipe off any flung out lube the wheel stays vastly cleaner.

I suspect a reason why IGH manufactures have more and more gone to no oil hole design (and that indicator hole in the axle doesn't count here) is because they don't have faith in the general public to routinely oil their oil only hubs every so often. By closing up the hub better and using a grease (and sometimes a "special" grade of grease) they extend the life of the factory lubing. Still on my IGHs, and those others I have serviced, I do add oil through the axle's hole. Just not too much. SA use to suggest a few drops of oil annually as one example of volume and frequency for their non grease hubs. Andy