The shear relaxation spectra of various lubrication oils were measured at 5-205 MHz and 10-70 degrees C, and the variation of the steady-state shear viscosity (eta(0)) was divided into the contributions of the high-frequency shear modulus (G(infinity)) and relaxation time (tau). The temperature dependence of eta(0), was dominated by that of tau. The increase in molecular weight accompanies both increase in tau and decrease in G(infinity), and the increase in eta(0) results from the larger effect of the former. The flexibility of the chain reduced tau, while its effect on G(infinity) was rather small. The introduction of phenyl or cyclohexyl groups enhanced G(infinity). Oils of larger G(infinity) tend to exhibit a larger temperature dependence of eta(0).