The behavior of a rotating system after its power supply is cut off is called the coastdown phenomenon. An experimental investigation of the coastdown characteristics was carried out on a rotor rig, with different types of lubricants including a Newtonian oil, a.blend of ISOVG 32 and hydrogenated styrene isoprene, multigrade oils, and aqueous polymer solutions in a hydrodynamic journal bearing. The characteristics were plotted in terms of deceleration vs. speed, which resembled the Stribeck diagram of friction due to viscous drag. Thus, the apparent Stribeck diagrams of friction for the above oils were obtained by plotting the derived coefficient of friction against the reciprocal Sommerfeld number. Theoretical results were obtained through the solution of the governing Reynolds equation and energy equation, for Newtonian and cubic law fluid models. The experimental results are compared with the respective theoretical results for the case of friction in journal bearings lubricated with non-Newtonian fluids. © 1993 Taylor & Francis Group, LLC.