What grease/oil for smoother focusing?

I bought a Carl Zeiss Jena 135mm a while ago. When I got it, it was in need for a thorough cleaning. So I followed this disassembling guide: http://www.andrew.brown.dsl.pipex.com/articles/czj135svc/
Note that I did not follow the guide when it came to de- and regreasing all threads; I left the old lubricant untouched.

Although the lens now is functioning well, the focusing ring is pretty slow. I have made the conclusion that it's the lack of lubricant between the focus guiding rods (red arrows, first picture) and the rod 'railings' (blue arrow, second picture), because the focusing is amazingly smooth when the guiding rods are disconnected.


I don't know if it's grease or oil that is suited for this task, but I am however looking for a lubricant that any of you here on Dyxum have tried on your own lenses with success. I'm afraid of using something that might run inside the lens or release fumes.

Thanks for the link, Waleskeg. How much do you think would be enough to put on there? From what I can see, there are not really any grease in the "guide railings". However, I think there is some kind of oil there because touching there leaves a dark residue.

Also, should I remove whatever lubricant that is on the rods/railings before I apply the new one, or is it not necessary?

romke wrote: it is best to remove all original grease or oil. probably it has deteriorated over time (oxidation) and its (present) composition may well not be compatible with the new lubricant. also be aware that most lubricants used for this type of equipment do have a composition that may be vastly different from say standard engine oil or wheel bearing grease (not based on mineral oil) - so you should avoid standard lubricants. enough is enough - and if you can clearly see the lubricant it usually is far more then enough....even the moving parts of the engine in your car are sufficiently lubricated with a lubricant film of say 60 micron or less....in other words: don't overdo it.

Will it be necessary to do make a hot bath with soap to remove that grease, like in the cleaning guide? I would rather not have to regrease the focusing threads as well, only the railings. Do you think I could just wipe the railings with a q-tip?

After re-examining the lens and the railings, I used a q-tip to see if there actually was any lubricant present. The rod and railings are more or less clean, only a fraction of dark residue showed up(I would guess it's old oil).

The focusing is not stiff, but more sluggish, and there are no grinding sounds. However, it takes some torque to turn the focusing ring on the lens, more than what I would consider normal, and it makes focusing while recording video very hard and unstable.
I'm starting to wonder if there ever was any lubricant between the rods and the railings, but the focusing is really not as smooth as I want it to be.