What’s the best lubricant to use for Z-axis lead screw and guide bars?. Our newly received Mbot Grid Dual is making an annoying screeching sound whenever the build platform moves quickly up or down, like during homing. The lead screw and guide bars seem dry like they never got pre-lubed by the manufacturer. I’ve tried applying some of the lubricant that was provided in the tool kit, but it’s still screeching. I don’t want to over-lube it and cause other problems.
I’ve used bycycle chain lube and some Teflon grease. I would’nt use the grease anymore as it can stick to other places. just one drop of oil is enough. may be you Need first to check the z-axis if the screw aren’t not to tight or to loose. To loose and the plate is “wobeling”
I read on another site that Super Lube was a good product to use. It’s a synthetic lubricant with PTFE. I picked some up from Harbor Freight.
I’ve heard 3-in-1 oil or sewing machine oil.
…except, 3-in-1 is petroleum based, which would probably be bad for plastic, like the bearing holders and other parts of our printers. Perhaps a silicone based lubricant instead, as davensac suggested.
if there still is noise after you have put the lubricant on it ,you can try to adjust the screws here 
