Do I need to use rinse aid even if my detergent already contains it?

Yes, to achieve proper drying, always use a liquid rinse aid even if your detergent contains a rinse aid or drying additive. Using no rinse aid or setting the dispenser to 0 may result in longer cycle times consuming more energy and water, and the higher temperatures and longer cycle times can damage fine china or glassware. (Page 12)