thanks for the replies. Although I got a mix of answers - the hub uses oil, the hub uses grease, it does make sense that the 3S originally used grease - otherwise there should be an oil port on the hub like the other older Shimano hubs (333)? That's too bad, in my opinion. Although you wouldn't need to lubricate with grease nearly as often as oil, if you buy a used bike with the 3S and can't find out it's history on this, you would, more than likely, have to go through the trouble of opening everything up, cleaning out the gunk and re-greasing. And with virtually no technical data/diagrams etc on the 3S, I personally wouldn't want to do this. I'm a beliver in "if all else fails, follow the procedure". Problem is, there is no procedure.
Thanks again - I think I'll just steer clear of this Shimano hub.