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The majority of low sulphur automotive diesel fuels marketed today are treated with an additive to enhance the lubricity of the base fuel. Field experience has shown that in order to achieve the full benefits of the low sulphur diesel fuel, the lubricity additive must not only provide sufficient lubricity performance to protect sensitive diesel fuel pumps, but must have no undesirable side effects. These potential side effects include: 1) Degrading the properties of the base fuel, 2) Interacting with crankcase lubricating oils, 3) Reducing the performance benefits of other fuel additives The oil and additive industries have developed a wide range of tests to evaluate the no-harm performance of lubricity additive packages and components. This paper describes many of these tests, with respect to their use in the development of a novel, lubricity additive package for City Diesel Fuel.

Considerable development effort has shown that conventional diesel engine lubricating oil specifications do not define the needs for acceptable injector life in methanol-fueled, two-stroke cycle diesel engines. A cooperative program was undertaken to formulate an engine oil-fuel additive system which was aimed at improving performance with methanol fueling. The performance feature of greatest concern was injector tip plugging. A Taguchi matrix using a 100 hour engine test was designed around an engine oil formulation which had performed well in a 500 hour engine test using a simulated urban bus cycle. Parameters investigated included: detergent level and type, dispersant choice, and zinc dithiophosphate level. In addition, the influence of a supplemental fuel additive was assessed. Analysis of the Taguchi Matrix data shows the fuel additive to have the most dramatic beneficial influence on maintaining injector performance.