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A bench test was performed with Toyota 1500 cc OHC engines using a modified AMA mode in order to determine the change in performance, such as oxidation stability, thermal stability and antiwear performance, of gasoline engine oils as a consequence of their degradation. For the purpose of analyzing the relationship between the degradation of engine oils and their performance in detail, engine tests were performed without any new oil supply. The remaining performance of used oils was discussed in connection with both the degradation of engine oils and the depletion of oxidation inhibitors. The oxidation inhibitors, such as ZDTP, diarylamine and high molecular weight phenol, remaining in used oils were measured quantitatively with liquid chromatography. Oxidation stability, thermal stability and antiwear performance were measured with TFOUT, the hot tube test and the four ball test, respectively.

Detergent additives in automotive gasoline fuel are mainly designed to reduce deposit formation on intake valves and fuel injectors, but it has been reported that some additives may contribute to CCD formation. Therefore, a standardized bench engine test method for CCDs needs to be developed in response to industry demands. Cooperative research between the Petroleum Association of Japan (PAJ) and the Japan Automobile Manufacturers Association, Inc. (JAMA), has led to the development of a 2.2L Honda engine dynamometer-based CCD test procedure to evaluate CCDs from fuel additives. Ten automobile manufacturers, nine petroleum companies and the Petroleum Energy Center joined the project, which underwent PAJ-JAMA round robin testing. This paper describes the CCD test development activities, which include the selection of an engine and the determination of the optimum test conditions and other test criteria.

The effects of lubricant composition on low temperature wear were studied in low-to-medium temperature cyclic mode engine tests fueled with M-85. The wear characteristics on the cylinder bore, piston rings, bearings and cam lobes were dependent on the lubricant formulations, in particular the detergent chemistry. Calcium borate overbased detergents were found to be suitable for formulating methanol-capable automotive lubricants. Cylinder bore wear could be prevented by preserving the alkalinity of the lubricants during the tests. Valve train wear in M-85 engine tests was correlated with JASO motor-driven valve train wear tests using emulsified oils. The piston ring wear was at a similar level to that of gasoline fuels. Bearing wear was not significant and could be well correlated with the wear scar of the used oils measured with the four ball tests and was found to be of an abrasive nature.

The effects of gasoline volatility (T50 and T90), sulfur content and hydrocarbon types on CO, NOx, total hydrocarbon and speciated hydrocarbons were investigated. The properties of the test gasoline were varied in the range of the Japanese marketplace gasoline, which are characterized by low T50, T90 and low sulfur content. Sulfur content is, especially, regulated under 100 ppm. The Japanese 10.15 mode emissions under hot-transient conditions were measured by using a vehicle equipped with a three-way catalyst. The results indicated that the sulfur content was more effective on exhaust CO, total hydrocarbon and NOx emissions than T50, T90 or hydrocarbon types of gasoline were. The sensitivity to sulfur was different depending on the speciated hydrocarbons. Increasing the sulfur content significantly raised exhaust paraffines, but had no significant effect on olefins. Among the aromatics, the exhaust benzene was most sensitive to sulfur.