The drag reduction (DR) of nonionic surfactant (oleyldimethylamine oxide, ODMAO) in ethylene glycol (EG) aqueous solutions was investigated at the solution temperature of 20 ºC. The pressure drop and flow rate were measured in the pipe flow system with the inner diameter of 5 mm. The concentration of ODMAO solutions was 1000, 2000, and 3000 ppm by weight. Regardless of the ODMAO concentration, the DR could not be obtained in EG aqueous solutions, in which the concentration of EG was fixed at 30 % by weight. It was revealed, however, that the addition of a small amount of salicylic acid noticeably improved the drag-reducing ability at the ODMAO concentration of 2000 and 3000 ppm even in the 30 % EG aqueous solution, as well as the pure aqueous solution, in which the higher DR was achieved at the lower concentration.
