Low Viscosity Oil Studies and the Influence of Radial Clearance on Bearing Distress in a 3.8L Engine 880682
Classical journal bearing equations predict the function of oil flow in dissipating heat, thereby governing the effective viscosity of the lubricant in bearings. From this perspective, experimental dynamometer tests explored low speed, high load, high temperature, operation of four low viscosity oils. Test length was 48 hours using a 3.8L V-6 engine under steady state and cyclic conditions.
With a 1.4 cP HTHSR viscosity oil the bearing distress appeared dependent on connecting rod bearing clearances serving to govern rate of oil flow through the main bearings. Front and rear main bearings exhibited severe overheat-distress. This was related to the design of the oil distribution system in the crankshaft. A severe cyclic acceleration test showed little bearing distress. Significant distress occurred only with an SAE 5W viscosity grade. SAE 5W-30 and 5W-40 multigrades showed no abnormal wear. Results were interpreted in terms of high temperature, high shear rate rheology of the test oils.
Citation: Heath, D., Baczek, S., and Sterlekar, T., "Low Viscosity Oil Studies and the Influence of Radial Clearance on Bearing Distress in a 3.8L Engine," SAE Technical Paper 880682, 1988, https://doi.org/10.4271/880682. Download Citation
D. H. Heath, S. K. Baczek, T. J. Sterlekar
The Lubrizol Corp.
SAE International Congress and Exposition
SAE Transactions Journal of Fuels and Lubricants-V97-3