MINIATURIZATION OF LUBRICANT DEGRADATION TESTING FOR NATURAL GAS ENGINES

Lubricant evaluation in natural gas engines is expensive due to large sump volumes and high equipment costs. A new laboratory protocol was developed to miniaturize oil degradation conditions in order to provide a rapid screening method for lubricants. Steel coupons were coated with 200 mu m films of three commercial lubricants for natural gas engines. The films were oxidized for up to 90 hrs at 150 degrees C, 180 degrees C or 200 degrees C, then their tribological properties were compared using ball-on-plate tests. No deterioration in tribological performance could be noticed after film oxidation. Sump drains of the three lubricants were also obtained from actual engines with service life in excess 5000 hrs. Only slight reduction in tribological properties was observed, despite dropping alkalinity. This testing protocol can be further refined and possibly applied in lubricant industry, where it would reduce development time of natural gas engine lubricants and further improve their effectiveness.