I have some 1U Rapid Rails (for PE1650's / PE850's) that are starting to get a little sticky when pulling them out.  As the 1U rails do not get the benefit of ball bearings or rollers, I figure i'm going to need to lube them up so they'll slide smoothly again.  What is the best lube recommended for these types of rails?  my short term fix is a squirt of WD-40, but my experience with rails indicates a thicker, almost gel/grease type material - again no idea what Dell or other rail manufacturer's use.

Any information would be very helpful.

Thanks

B