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In Japan, turbocharged passenger cars have recently been introduced with increased improvements in fuel economy and engine performance. However, a turbocharger is driven by hot exhaust gas, so that an engine oil with superior thermal stability is required. After studying a turbocharged engine's thermal effects, two laboratory screening tests that correlate with dynamometer engine tests were established. These tests, termed the panel coking test and the high temperature panel corrosion test, enable one to evaluate base oils, additive components and viscosity index improvers for a given engine oil. Finally, a 10W-30 engine oil formulated by using these tests, showed superior deposit control and anticorrosion performance in the dynamometer engine test and actual driving conditions.

A bench engine test for evaluating the fuel efficiency of automotive crankcase oils using modern engines was developed. The fuel consumption was primarily proportional to the viscosity of the oils down to 5 mm2/s at operating temperatures, indicating that the use of low-viscosity oil was effective in improving fuel efficiency. This may be because the oil film would be formed easily, since sliding parts, such as valve train systems, in modern engines are finely finished. Organo molybdenum dithiocarbamates were effective in improving fuel efficiency at high temperature. A 2.7% improvement in fuel efficiency relative to conventional SAE 10W-30 oils was achieved by the combination of low-viscosity SAE 5W-20 oils and organo molybdenum dithiocarbamates under constant operating conditions with engine speed 1,500 rpm and torque 37.2 N•m.

A high viscosity index (HVI) petroleum base stock (VI=125), which is produced by a severe hydrocracking process, has been used in formulating an advanced SAE 5W-30 oil meeting API SG, EC-II and current ILSAC performance requirements in order to demonstrate potential fuel economy benefits of this oil. The oil was formulated by blending the HVI base stock with a small amount of a solvent-refined base stock to obtain an “optimal aromaticity”, a dispersant VI improver, an optimized combination of detergent and inhibitor, and a conventional ashless friction modifier. The fuel economy performance of this oil has been compared to that of a similarly formulated solvent-refined SAE 5W-30 oil using the Sequence VI test, a motored engine friction test, a new fired/motored friction test, and the EPA road simulator fuel economy test. The SAE 5W-30 HVI oil exhibited an improved fuel economy performance in the above tests, despite of higher HTHS viscosity of the HVI oil.

In Japan, test methods for evaluating the performance of 2-cycle engine oils have been developed separately by each 2-cycle engine manufacturer. The reason for this is that there are are many differences in engine performance and in lubrication methods. Evaluation through bench tests is used as a valid method for screening engine oils prior to field tests. Field tests are conducted eventually as the most reliable test method for evaluating the performance of engine oils. Yamaha Motor, one of the leading Japanese 2-cycle engine manufacturers, developed a “70 min engine test method” in 1963, which can be conducted in a relatively short period of time with good reproducibility. In this paper, several problems regarding Yamaha's 70 min engine test method are discussed.