Lucas themselves said "light machine oil".

You're lubricating the ring-shaped felt pad.



This is why the correct original 200354 end caps for this period have a brass lubricator cover plate. (pre-war dynamos had a small spring-loaded push type lubricator).



A lot of pattern end caps have no lubrication facility. I dodn't know what the thinking is, or if they reflect post-war practice and Lucas ceased to fit them.

With no oiler on the cover, it is necessary to release the cover and give a drop or two from the "Wesco".

Many thanks Rik, very helpful. I'll take the end cap off and grab the 3in1
cheers
Dean

Well, I've removed the end cap to find there is no felt. I can see a bearing but this appears to be sealed. I could try and get a felt or make one but if the bearing is sealed ther seema little point.
I am glad I took the end cap off because there is quite a bit of corrosion in there so needs a spray of water repellent oil?