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The friction reducing potential of low viscosity engine oils in bearings has been investigated using a journal bearing test rig. Friction was measured on both the journal and bearing of a production connecting rod and compared to results from a simple analytical model over a range of speeds and loads. Hydrodynamic lubrication conditions existed over most test conditions, but mixed lubrication conditions were shown to exist at low speeds in heavily loaded journal bearings. Results indicate significant friction reduction through the use of low viscosity oils under hydrodynamic lubrication conditions. In mixed lubrication conditions, oils with friction reducing additives exhibit lower friction than those without such additives. These findings suggest the possibility that a low viscosity oil with effective friction reducing additives can extend low friction benefits over the entire range of operation of engine bearings.