Crumb rubber–modified asphalt (CRMA) extensively suffers from high-temperature storage instability. Because of the higher density of the crumb rubber modifier (CRM) particles, they settle down to the bottom of storage tanks and cause variation between physical properties of the top and bottom samples. The storage stability of the CRMA changes under different interaction parameters and consequently different mechanisms of interaction. In this research the mechanism of separation under different levels of CRM dissolution was investigated by using Stokes’ law. The extent and mechanism of CRM dissolution in asphalt was controlled through regulating interaction temperature and inter action mixing speed. A standard storage stability test was conducted on CRMA samples to measure the corresponding storage stability index. Viscosity of the liquid phase of CRMA was measured at the same temperature as that of the storage stability test (163°C), with the use of a rotational viscometer, to study the effect of viscosity development of the liquid phase on the storage stability of CRMA. Composition analysis was conducted by using thermogravimetric analysis to investigate the effect of changes in CRM composition on the storage stability of CRMA. Results reveal that, in addition to the CRM particle size reduction resulting from CRM dissolution, the viscosity development of the liquid phase affects the storage stability of CRMA with the interaction temperature of 190°C. But increasing the interaction temperature to 220°C changes the mechanism of dissolution and the nature of the residual CRM particles and consequently leads to a different mechanism of separation.