Seiko's technical guide recommends S-6 silicon grease for the second reduction wheel and it would seem some of you would prefer a thicker oil like D5 or HP-1300 whereas @jdm and @CaptCalvin prefer a grease. According to CousinsUK 8301 contains graphite and is similar to Seiko S-4 and is the recommended grease for the first reduction wheel.
Hmm... Since S-6 is a grease I believe a grease would be the better option. So, how about some Moebius 9501 as I have it?
We had another member recently looking for reassurance about using Seiko lubricants, but no amount of good reasoning prevented him from spending on that. Probably caused by blind faith in written material over relying on other's experience when it comes to a question asked many times on this forum alone.
I use 8301 there. A bit messy and natural based, still better than leaving it dry like the factory does.
I don't think you can really pump in oil in there since the air trapped in prevents that. And any oil left on the flat facing the balance is count productive. So the fine applicator is used to push some oil in the hole. That is my understanding at least.
Rub-in jewels have integrated end stone, out of obsession I am always concerned if I have managed to get enough oil on its end stone, automatic oiler seem assuring to have dispensed that certain amount of oil there, one can double the amount by pumping twice and the exactness of the amount is a nice control to have.
In a sense, same story with screw on end stones, you can just screw the end stone on and then oil. Much neater outcome since end stone plate/ holder is sure to move when you try to place it on and oil gets spread around by the old method.
I use old accupuncture needles as oiler.