I had a Taz 5 for a few months before getting the 6. One thing I noticed on the 6 is the Z axis screws aren’t lubed like the T5 was. On the T5 there was visible white grease on both Z axis screws, but nothing visible on the 6. Nothing noticeable comes off when wiping them either. Should there be?
I have white grease on mine! 
From the factory?
No need to lubricate TAZ 6 z lead screws. They are now stainless steel too.
Good to know, thanks!