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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.

The Ball Rust Test (BRT), a corrosion bench test developed for evaluating the rust preventing qualities of crankcase motor oils, is being proposed as a replacement for the ASTM Sequence IID engine test. Details of this bench test are described in the paper “Development of the Ball Rust Test - A Bench Test Replacement for the Sequence IID Engine Test.” In this paper, a good correlation was established between rust performance in the BRT versus the IID engine test rust rating for a variety of oils. Following the development of the BRT, a comprehensive study was conducted using this bench test to define the effectiveness of oil additive type and concentration on rust inhibition. This paper summarizes these results and offers insight into effective rust control in a corrosive environment. High-base metallic sulfonates were found to be most effective at preventing rust primarily due to preservation of alkalinity.