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Soot-related oil thickening problems have been reported over the years by multiple OEMs in Europe, Japan, and in the U.S.A (1,2,3). The earliest problems, from the late 1970s, were often attributed to adverse changes in operation [lower engine speeds, heavy loads and low air/fuel ratio, or severe operation such as stop-and-go service (3)] which led to a high soot generation rate. In the late 1980s, the emission legislation became more stringent and soot-related oil thickening concerns resurfaced. It appeared that even engines that produced a relatively low level of soot in the exhaust gas showed a high level of soot contamination in the lubricant (4). For the oil and oil additive industry, the Mack T-7 engine test offered a useful tool to evaluate the ability of oils to disperse soot, but it has been noted that the industry remains without a test based on a European engine to adequately evaluate an oil's ability to disperse diesel engine soot.

An electronic engine management system has been developed to control both ignition timing and air-fuel (A/F) ratio to maximize fuel economy. Both controls employ feedback techniques and are therefore intrinsically adaptable to a wide variety of models, as required for a universal retrofit market. The ignition control loop monitors the position of the combustion pressure peak while the mixture control loop senses the lean limit as defined by a roughness threshold. Test results demonstrate fuel economy and transient operation. A brief background to the New Zealand energy conservation program is in included as background to the system’s specification.