Should I lubricate rear derailleur wheels Replacing the chain I found  that the plastic wheels of the rear derailleur are rotating with high resistance.

So I disassembled the wheel, cleaned it from dirt and sprayed with WD-40. Here is how it looks now:



I have Motul Tech grease 300, that I used to lubricate the ball bearings in the hub. So, should I put the grease between the steel cylinder (how is it called?) and the inner round hole of the wheel?

Or it will just attract dirt and make things worse?
Usually if they're turning as you describe with high resistance, they're either gunked up and need cleaning or they're put together wrong. They should spin very freely without any added lubrication. Grease would probably tend to do as you say and attract dirt, but a thin coating on the outside of the bushing isn't going to ruin anything if you want to try it. I do a drop of light lube at the gap of each one to keep them running quietly, but it's usually a negligible difference either way.