Besides the ASTM chart mentioned above you can look for the BP viscosity/temperature chart based on log log(visc +0.8), as function of log T, where visc is in cS, and T is absolute temperature (the chart also gives oC and oF scales).
Same chart offers blending possibilities by w%, as well as various viscosity scales: Saybolt Furol seconds, Saybolt Universal seconds, Engler degrees, Redwood 1 seconds, and, of course, kinematic viscosity in centistokes.