An expression is suggested for correlating viscosity and kinematic viscosity data over a wide range of pressure and temperature. This expression is obtained by expanding the natural logarithm of viscosity in a series about ambient pressure and temperature. This series expansion is truncated to obtain a relatively simple relation that contains several useful empiricisms as special cases. Coefficients in this expansion are conveniently determined using a regression analysis. The proposed relation describes ASME data for several oils to within a 3 percent average deviation for pressures to 350 MPa (50 ksi) and temperatures to 373 K (100°C). The average deviation is less than 15 percent for pressures to 1.0 GPa (150 ksi) and temperatures to 491.5 K (218°C). In both cases, the agreement is typically much better than those predicted by other correlations over the same range of pressure and temperature.