The kinematic viscosity of biodiesel and its blends with diesel fuel

As the use of biodiesel becomes more widespread, engine manufacturers have expressed concern about biodiesel's higher viscosity. In particular, they are concerned that biodiesel may exhibit different viscosity-temperature characteristics that could result in higher fuel injection pressures at low engine operating temperatures. This study presents data for the kinematic viscosity of biodiesel and its blends with No. 1 and No. 2 diesel fuels at 75, 50, and 20% biodiesel, from close to their melting point to 100 degrees C. The results indicate that while their viscosity is higher, biodiesel and its blends demonstrate temperature-dependent behavior similar to that of No. land No. 2 diesel fuels. Equations of the same general form are shown to correlate viscosity data for both biodiesel and diesel fuel, and for their blends: A blending equation is presented that allows the kinematic viscosity to be calculated as a function of the biodiesel fraction. Paper no. J9166 in JAOCS 76, 1511-1513 (December 1999).