We investigated the influence of three different paraffin chain sizes (C22, C28, and C36) on the outflow profile of oil dissolved in mineral oil using thermal lens spectrometry (TLS) coupled with laser-induced fluorescence spectrometry (LIFS). The data show that the presence of paraffin molecules leads to an increase in the fluorescent quantum yield of natural oil probes, as observed by the reduction of the photothermal signal and the consequently increased fluorescent emission. We also observe that larger paraffin molecules such as C36 tend to move toward the bottom layer during the fluid outflow. This may be associated with the nucleation process and formation of paraffinic deposits in oil ducts. (C) 2015 Elsevier Ltd. All rights reserved.