Window guide lubrication

My drivers door window labours. I thought it was the motor, but when I disconnected the glass and supported it the mechanism worked ok, but with the mechanism down, it is difficult to push the glass down, there is a lot of resistance in the front guide, and when I put my hand in the door and feel the guide it feels sticky. Do they degrade, and any suggestions as to what I could use to lubricate it, or do these need replacing after 15 years?

Silicone lube works well, Maplins online or Robert Dyas sell it in spray cans.

I have used a white synthetic grease from Kluber called Isoflex. It does not degrade and is a "clean" lubricant with great adhesion. Once applied it should last for ever.

Sundance

https://www.klueber.com/uk/en/products-service/products/isoflex-topas-nb-152/10336/

Thanks both. I took the cheater out today and gave the runner a good spray with silicon grease and adjusted the window, appears to be running better now.