Abstract Pressure drop and homogenization efficiency of a motionless mixer of helical type have been studied experimentally. For evaluation of the drag coefficient the equation has been proposed which is valid within the range of Reynolds number from 10−2 to 104 The efficiency of the motionless mixer for mixing of two Newtonian liquids has been investigated by using a decolourization method. For the operating conditions studied in this work it appears that there is the worse performance of the mixer about the Reynolds number of 50. No influence of volume flow rate ratios (from 1 to 10) upon the performance of the mixer has been observed. A higher number of mixing elements must be applied for homogemzation of liquids with viscosity ratios above 100 as compared with that for viscosity ratio 1.