Abstract
As mileage accumulates, a gasoline engine tends to require a fuel of higher octane number due to an octane requirement increase (ORI). It is a generally accepted concept that ORI is caused almost entirely by combustion chamber deposits. Although much work has been done on the possible influences of the deposits on ORI, the quantitative aspect of the influences of deposits was not entirely clear. Thus, in order to clarify their influences on ORI, a study was made under accelerated conditions, using a minitype engine test, which was developed in this laboratory during the present study. Some of the relevant information obtained in this study are as follows: ORI was proportional to the amount deposited; fuel and lubricant influenced almost equally to the deposit buildup; the effects of oil consumption and Conradson carbon residue (CCR) of the lubricant on the deposit buildup and on ORI were found significant.
The mini-type engine test was found to provide an effective method to investigate ORI problems related to fuels and lubricants without the needs of involved deposit-accumulation procedures.
