It is important to keep sleeves, collars and oarlocks clean and grit-free in order to ensure smooth feathering action and long life. It is not necessary to lubricate these plastic components, but if you choose to, use a light silicone lubricant or WD-40. If you use oil or grease, wipe it off frequently. Oil and grease tends to attract and hold grit, which will prematurely wear the sleeves, collars and oarlocks.
You can significantly reduce collar wear by using CLAMS on your oars. Note that the collar is symmetric and can be used in either direction. When one side shows wear, extend its use by flipping the collar and using the other side.