Drag reduction caused by surfactant solutions is considered to be an effective way to reduce the running cost in closed-loop district heating and cooling systems. Conversely, much research has pointed out that heat transfer reduction occurs simultaneously for drag reducing flows. In this study, drag reduction and heat transfer characteristics were measured for drag-reducing additives with two cationic surfactants of different concentrations, particularly in a higher temperature range, that cross the upper limit temperature of drag reducing solutions. Information on what occurs at this higher temperature range is necessary for design and operation with considering heating processes.