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An examination was made on the effect of low-viscosity engine oil on fuel efficiency improvements and engine reliability for the purpose of improving fuel efficiency through the use of select engine oils. Fuel efficiency-improving effects were estimated by measuring friction torque using low-viscosity engine oil. The results show that reducing engine oil viscosity is effective for improving fuel efficiency. In examining engine reliability, attention was paid to the following two aspects which are concerns in practical performance that may arise when engine oil viscosity is reduced. Engine oil consumption Sliding wear at high temperatures Tests and analyses were conducted to develop indexes for engine oil properties that are strongly correlated with each of these two concerns. A strong correlation was found between engine oil consumption and the results of a thermogravimetric analysis, and between high-temperature sliding wear and high-temperature, high-shear viscosity (HTHS).

The relationship between gasoline properties and vehicle particulate matter emissions was investigated, for the purpose of constructing a predictive model. Various chemical species were individually blended with an indolene base fuel, and the solid particulate number (PN) emissions from each blend were measured over the New European Driving Cycle (NEDC). The results indicated that aromatics with a high boiling point and a high double bond equivalent (DBE) value tended to produce more PN emissions. However, high boiling point components with low DBE values, such as paraffins, displayed only a minor effect on PN. Upon further analysis of the test results, it was also confirmed that low vapor pressure components correlated with high PN emissions, as might be expected based on their combustion behavior. A predictive model, termed the “PM Index,” was constructed based on the weight fraction, vapor pressure, and DBE value of each component in the fuel.

Research was conducted on cold startability with a focus on the vaporization characteristics of ethanol blended fuel (E85). Cold startability was tested with a conventional gasoline engine with standard calibration data by using gasoline and E85 of which RVP is adjusted to be equivalent to gasoline. The test engine started successfully when the gasoline was used, but failed to start when the E85 was used. A further analysis of this result indicated the fact that E85 displays lower vaporization than gasoline under cold conditions even if the RVP of both fuels are the same. The research determined that the formation of an air fuel mixture with minimum of 2 vol% fuel concentration is necessary for a successful engine start. The effects of increasing compression ratio and cranking speed as means of enhancing fuel vaporization were investigated and no major impacts ware observed.