If you have the typical rack & pinion slide, where a toothed sliding rail is moved by a geared motor, no lubrication is needed. In fact, most manufacturers recommend against it, since the lubricant picks up dirt that will cause more wear than if the metal is just left alone.
If you feel you must lube it, use a rapid dry silicone that does not leave a sticky surface.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL