I don't have any of those bikes but I've had a Nexus 8 and now have an Alfine 8. They do use grease for lubrication but you can use an "oil bath" instead using either Shimano's oil or ATF fluid.

Basically you pull the innards out, let them soak in the oil for awhile, then put it back together. I believe that should be done every couple of years depending on your riding habits and conditions. I recommend it. The grease gets a little thick in cold weather. It might be my imagination but I can feel the difference.