The text below is from the Lippert web site for the slides on Diplomat and Endeavor. The Operation and Service manual can be viewed at:
http://www.lci1.com/Service%20Owners%20Manuals/Slideout...c%20Slideout-Web.pdf
"When the room is out, visually inspect the Inner and Outer Rail Assemblies.
Refer to Fig. 1 for location of inner rail assemblies. Check for excess buildup
of dirt or other foreign material; remove any debris that may be present.
"¢ If the system squeaks or makes any noises it is permissible to apply a coat
of lightweight oil to the drive shaft and roller areas but remove any excess oil
so dirt and debris do not build-up. DO NOT use grease."
Mine were beginning to make some noise and I cleaned and lubed them. Not sure how much it reduced the noise but I felt better. I used the PacBrake silicon lube. No specific reason, I have a bottle of it and it was available. It is pretty light weight and does not contain petroleum distillates.
Hope this helps,
mark