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This paper reviews the development of a new standard for four-stroke diesel engine oils, JASO DH-1 (JASO M355: 2000). This standard was introduced to the market on April 1, 2001. It prescribes the minimum performance for engine oils conforming to four-stroke diesel engines manufactured by Japanese OEMs. This standard is composed of four engine tests and seven bench tests. The engine tests include a piston detergency test (JASO M336: 1998), valve train wear test (JASO M354: 1999), soot dispersancy test (ASTM D 5967-99) and high temperature antioxidation test (ASTM D 5533-97a). The piston detergency test and the valve train wear test were developed in Japan. The bench tests measure hot surface deposits, anti-forming, volatility, anti-corrosion, shear-stability, total base number, and seal compatibility.

The purposes of this paper are to develop a new laboratory oxidation stability testing method and to clarify factors relative to the viscosity increase of engine oil. Polymerized products, obtained from the oil after a JASO M333-93 engine test, were found to consist mainly of carboxyl, nitrate and nitro compounds and to increase the oil viscosity. A good similarity between the JASO M333-93 test and the laboratory simulation test was found for the polymerized products. The products were obtained not by heating oil only in air but by heating oil while supplying a synthetic blowby gas consisting of fuel pyrolysis products, NO, SO2 and air. The laboratory test has also revealed that the viscosity increase depends on oil quality, organic Fe content and hydrocarbon composition in the fuel. Moreover, it has been found that blowby gas and organic Fe accelerate ZnDTP consumption and that aromatics concentration in the fuel correlates with the viscosity increase of oil.

It is widely known that pellet-typed catalysts are deactivated by phosphorus (ZnDTP) that comes from engine oils. In this paper, the poisoning of monolithic three-way catalysts and oxygen sensors by engine oils is studied. First, catalysts and oxygen sensors were poisoned on the engine bench by test oils in which the quantity of phosphorus and ash was varied. Next, performance of the catalysts and sensors alone was examined and the vehicle exhaust emission at FTP mode was measured on a chassis dynamometer. The results indicate that phosphorus in engine oils poisons the monolithic catalyst and the oxygen sensor resulting in deterioration of the vehicle NOx exhaust emission. However, Ca sulfonate and Mg sulfonate detergents act by restraining phosphorus poisoning of the catalyst and the oxygen sensor. Through analysis of the catalyst and sensor surfaces, it is concluded that phosphorus poisons the catalyst and sensor forming a dense coating.