摘要 : Because of the impact of CO{sub}2 emissions on global warming there is growing concern to reduce the world-wide consumption of fossil fuels. An important way of achieving this is to increase the efficiency of internal combustion e... 展开 Because of the impact of CO{sub}2 emissions on global warming there is growing concern to reduce the world-wide consumption of fossil fuels. An important way of achieving this is to increase the efficiency of internal combustion engines in motor vehicles. This has led to the introduction of engine tests to measure the impact of engine lubricants on fuel efficiency and thereby assist in the design of lubricants to improve fuel economy. One effective way of formulating fuel-efficient engine oils is to include a small proportion of an oil soluble organo-molybdenum additive. This type of additive is able to react in thin film, iubbing contacts to form small platelets of the compound MoS{sub}2, which, because of their layer-lattice structure, give very low boundary friction coefficient. To make a useful contribution to engine fuel economy it is essential that friction-modifying additives continue to reduce friction throughout the engine oil drain interval. However, although friction-modifying additives are often very effecfive in reducing boundary friction and thereby increasing engine fuel economy in fresh oils, there are some doubts as to whether these additives are able to continue to reduce friction effectively in oils as these become progressively degraded during engine operation. Current and future engine oil specifications therefore include engine tests that measure fuel consumption both at the start and after prolonged running to assess the durability of fuel economy performance of engine oils. In a compaaion paper (Graham, et al.) the conditions under which fresh lubricants containing soluble organo-molybdenum additives are able to reduce friction were investigated. The current paper continues this study by examining the influence of lubricant degradation and rubbing time on friction reduction and thus the durability of performance of molybdenum additives. 收起