This work reports an experimental investigation of the oil segregation effect during the rheological evaluation of concentrated oil-in-water (O/W) emulsions. The results demonstrated that alkyl alcohols can significantly affect the rheological behavior of O/W emulsions. The addition of n-octanol and n-decanol to the emulsifying agent formulation produces a critical shear rate, promotes a sharp break in the flow curves and leads to a sharp viscosity drop, which was attributed to wall depletion. This phenomenon is related to the displacement of the dispersed phase away from the solid-boundary, which generates a low-viscosity oil-depleted layer that acts as a lubricating layer. The incidence of slippage depends on the alkyl-chain length and the concentration of the alcohol. The lubrication layer will promote energy savings during emulsified oil pumping and result in significant economic benefits to the petroleum industry. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.