I put new inserts in my tracks, and I'm glad I did. My seats move better. I
lube with heavy wax, the kind that is sold at hardware stores as "stainless
hinge lubricant". I beleive the reason for the inserts is the actual geometry
of the formed metal and the interference of sharp corners vs. radii. Hard to
explain, but close inspection of the assembled profiles will show you what I
mean. Also, I beleive the inserts to be impregnated with graphite.