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The Cummins M-11/EGR diesel engine test is a key tool in evaluating lubricants for the new PC-9 performance category. Wear on liners, crossheads, rocker arms and top ring faces of M-11/EGR high soot test engines operated with two different test cycles was studied through analytical surface techniques. The first test cycle used in this study was an early prototype PC-9 cycle, and the second test cycle was the PC-9 test procedure. Abrasive wear was observed on liners, crossheads and top ring faces. In addition to abrasive wear, corrosive wear was also found on M-11/EGR liners. However, no corrosive wear was observed on crossheads, rocker arms or top ring faces. Soot provides the major contribution to abrasive wear, since the widths of the relatively uniform parallel grooves in the wear scars closely match the primary soot particle sizes. More importantly, soot produced by the M-11/EGR engine was found to be harder than the engine parts.

The Cummins M-11 high soot diesel engine test is a key tool in evaluating lubricants for the new PC-7 (CH-4) performance category. M-11 rocker arms and crossheads from tests with a wide range of lubricant performance were studied by surface analytical techniques. Abrasive wear by primary soot particles is supported by the predominant appearance of parallel grooves on the worn parts with their widths matching closely the primary soot particle sizes. Soot abrasive action appears to be responsible for removing the protective antiwear film and, thus, abrades against metal parts as well. Subsequent to the removal of the antiwear film, carbide particles, graphite nodules, and other wear debris are abraded, either by soot particles or sliding metal-metal contact, from the crosshead and rocker arm metal surfaces. These particles further accelerate abrasive wear. In addition to abrasive wear, fatigue wear was evident on the engine parts.

Oil formulation has been found to be a significant factor in high rates of 6.2 L diesel engine, roller hydraulic valve lifter wear that occurred in field service with some commercial engine oils. This was confirmed through engine-dynamometer testing. A correlation has been established between engine-dynamometer wear test results and those obtained in laboratory four-ball wear tests conducted with used engine oil. The effects of dispersant level, viscosity, sulfonate metal type, sulfonate total-base-number, zinc dialkyl dithiophosphate (ZDTP) type, and ZDTP concentration on wear were systematically investigated. Wear increased with increasing soot concentration in the oil, and decreased with increasing sulfur concentration, both in the oil and on the metal surface. Wear also decreased with increasing dispersant concentration. The remaining oil variables had minimal effects on wear within the ranges studied.

The performance of various SAE 15W-40 and SAE 30. API CD/SF and API CE/SG oils was compared in on-highway vehicles with different diesel engines. The API CE/SG oils provided superior oil consumption control, better engine cleanliness, and less engine wear than the API CD/SF oils. Among API CE oils, a 1% sulfated ash formulation provided improved oil consumption and carbon deposit control compared to a 1.3% ash oil. One vehicle was extended to slightly beyond 1,000,000 miles, demonstrating that high quality, properly formulated API CE/SG oils can extend the useful life of an engine to overhaul.