Hypothesis: High temperatures can reduce the colloidal stability and rheological properties of nonpolar organoclay suspensions. The desorption of surfactants from organoclay has been proposed to explain this effect, but the mechanism remains unclear. In this work, it was hypothesized that the high-temperature induced desorption of ion-exchanged surfactants is the main factor affecting the stabilization of suspensions. Experiments: Using the cationic surfactant dimethyldioctadecylammonium chloride (DODMAC) and Na-montmorillonite (Na-MMT), the high-temperature-induced reestablishment of the adsorption-desorption equilibrium of DODMAC in organoclay suspensions was studied. Thermogravimetric analysis combined with infrared spectroscopy and gas chromatography/mass spectrometry experiments were performed to determine the thermal decomposition products and, ultimately, infer the adsorption modes and locations of DODMAC on Na-MMT. Thermal analysis and rheology were utilized to demonstrate the high-temperature-induced desorption and transfer of DODMAC in organoclay suspensions. Findings: High temperatures induced the complete desorption of physically adsorbed DODMAC molecules from particle surfaces, the partial desorption of ion-exchanged dimethyldioctadecylammonium ions (DODMA(+) ions) from particle surfaces, and the partial transfer of ion-exchanged DODMA(+) ions from the surfaces to the interlayers. Importantly, desorption of ion-exchanged DODMA(+) ions resulted in destabilization of the organoclay suspensions at high temperatures. (C) 2019 Elsevier Inc, All rights reserved.