AC/Heater vents in the dash hard to turn
 

Sometimes the vents in my dash do not like to turn -- like you do when you want the air to go up, or to the left, etc. But then sometimes they move quite freely. I'm sure it has something to do with temperature- cooler seems to move easier. (This is not the part you spin to close or open the vent.)

Has anyone else seen this?

Is there a lubricant I can use to fix it?

1984 300D

Try a silicone-based spray lubricant and use sparingly, it spreads much farther than you might like. Probably better not to get it all over the dash.