An elastohydrodynamic rolling disk test apparatus has been designed, built, and a matrix of traction data covering a range of loads, speeds, and temperatures have been obtained for 5P4E polyphenyl ether. Measured tractions are found to markedly increase with load and decrease moderately with rolling speed. The data show a very weak sensitivity to temperature. An apparent viscosity model has been advanced which uses an increased base viscosity and a decreased pressure coefficient of viscosity determined from the traction data to correlate the traction data and can provide a reasonable mathematical representation of the data.