I took my 2006 Prius in for its 30K mile scheduled maintenance today. The dealer suggested that I also get the PCV valve changed to prevent possible future oil overflow. This recommendation was in spite of the fact it is not part of the list of items in the scheduled maintenance for the Prius, and without first inspecting the valve to see if anything was wrong with it. They wanted to charge $100 extra, in addition to the $280 or so for the 30K mile maintenance. I have no idea what a PCV valve is and whether I need to get it changed. Can anyone comment on this? Why are they recommending it even though it is not part of the scheduled maintenance? Anyone else had this done? Anyone had problems due to not having it done? Thanks.