Temperature dependence of density and viscosity of vegetable oils

The straight use of vegetable oils as fuel in diesel engines entails adjusting several physical properties such as density and viscosity. By adequately heating the vegetable oil before entering the injection system, its physical parameters can reach values very close to that of diesel fuel. Consequently, by properly adjusting the temperature of vegetable oils used as fuel, it is possible to improve their combustion performance, thus avoiding premature engine aging due to incomplete burning. In this study the density and viscosity of several vegetable oils are studied within a wide variety of temperatures. The optimal range of temperatures at which each vegetable oil should operate in order to adjust its properties to those of automotive diesel and biodiesel is then found. Additionally an empirical relationship between the dependence of viscosity with density is presented. Thus, by means of the above-described relationship, through measuring the density of a given oil, its viscosity can be directly deduced. ► Vegetable oils density and viscosity are higher than the ones of diesel fuel. ► Density and viscosity have a deep impact on the combustion of existing diesel engines. ► Vegetables oils density and viscosity are reduced to match diesel fuel values by heating. ► The dependence between viscosity and density is modeled. ► It allows obtaining the viscosity from the measure of the density.