Waxy oil is a structuring medium due to crystallization of the paraffin components on cooling. Crystallization is a rather slow kinetic process. So the degree of crystallinity depends on the cooling rate and therefore the latter determines the rheological properties of oil. It is reasonable to suppose that the slower the cooling, the higher the degree of crystallinity and the higher the viscosity. However in reality the opposite is true: the viscosity of oil decreases when the cooling rate slows down. In this work, a model explaining this unexpected effect is proposed. The model is based on the relationship between the cooling rate and the temperature at which the viscosity increases unlimitedly. (C) 2015 Elsevier B.V. All rights reserved.