In this study, we investigated the influence of the number of ethanol (EO) groups of cationic surfactants having one oleyl group on the drag-reducing effect (DR effect). Also the effect of mechanical pumping power on DR effect was experimentally investigated using two experimental setups, a circulation system (with pump) and a pressurized once-through system (without pump). The concluding remarks obtained in this study are: 1. The DR effect strongly depends on the re-formation rate of micelles disrupted mechanically. 2. When increasing the number of EO groups of the DR surfactants from 0 to 2, the available temperature range of large DR effect was shifted lower. But the DR surfactant having three EO groups (EO-3) barely exhibited the DR effect even at the low temperature. This is because the big hydrophilic head of EO groups probably delays the re-formation of micelles disrupted by pumping power. 3. The DR effect was more liable to be influenced by pumping power with a decrease in temperature. This is because it takes a long time to re-form micelles disrupted by pumping power at low temperature.