In this paper, an equation to replace the well-known Arrhenius-type relationship was derived. This is because the activation energy constant is not yet in its fundamental form. The model maintains the traditional properties of activation energy and infinite-temperature viscosity constants, and it contains a new constant that is the zero-temperature viscosity. The ration of zero- and infinite-temperature represents the value of fundamental activation energy. This model was tested using six vegetable oils and has proven its accuracy (R-squared, 0.999). Viscosity – temperature stability refers to the difference between the zero- and infinite-temperature viscosities, rather than the activation energy.