Best lubrication for ball nuts

[Kitwn]

OK, I might as well get the embarrassing bit out of the way.
There's nothing wrong with one of my ballscrews. I thought I'd checked everything for tightness and was convinced it was the screw/nut at fault. But after loosening the flange fixing nuts to rotate the nut to see the tollerance mark Fred asked me to send him and re-tightening them...no play, no backlash, no problem.

I've apologised to Fred for the time wasted and saved myself about $75AUD. I've also learned that every ballnut, even on these basic cheap models, seems to be assembled specifically to suit the machining tolerance of the screw and has a number scratched onto it indicating the tolerance. I'm quite impressed by that, but it does mean you need to deal with one screw/nut at a time if you plan to take them apart for cleaning and not have just one tub full of all the balls from all your nuts.

I've gone for Valvoline chain oil for lubrication as there doesn't seem to be any single preferred option.