As far as I know, the lifespan of PVC windows is highly dependent on periodic lubrication. What kind of oil should I use to lubricate the moving metal parts of my PVC windows? Additionally, what should be the time span between two applications of the lubricant?
Quality sliding PVC windows use rollers. Keep the tracks clean, using a slightly damp lint-free cloth. The rollers take care of themselves.
On cheap PVC sliders, I use paste wax after cleaning the slot with a slightly damp lint-free cloth.
You can also use spray silicone. Clean the track with a slightly damp lint-free cloth. Spray the silicone on another lint-free cloth and wipe the track down.
Don't use any petroleum lubricants on PVC if you want it to last.