I need to redirect this question - I asked about what type of lubricant 
might make the sliding door quieter and it got focused on the wrong 
problem. 
Ask about lubricants and get:
1. Pee out the window
2. Use the front door
3. Take a porta Potty - or bucket.
<grinning broadly>

One more time folks - what kind of lube works best to quiet the sliding 
door? One thought of rubber wheels was interesting, but I don't think 
anyone has made that work - have they? 

-Jack