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In many countries, cetane number and distillation properties of diesel fuel have been changing, thus affecting the performance of diesel engines. This paper describes investigations made on the effect of diesel fuel quality on white smoke (one of the important emissions of diesel engines). The result of simple laboratory tests simulating high altitude conditions plus field tests using three types of disel engines supplied with various types of diesel fuels is given. It was found that white smoke appearing tendency correlated best with cetane number and the 90 percent distillation point of the fuel. The field tests performed at high altitude correlated well with the simple laboratory tests.

Engine dynamometer tests were conducted to evaluate the effect of detergent additives and gasoline components on Combustion Chamber Deposits (CCD). Additives with polyether amine (PEA) and with polyolefin amine (POA) chemicals were used. Three kinds of POA additives were used. Our results show that some kinds of additives and aromatics in gasoline increase CCD formation. Different polyolefin detergents show different tendency of CCD formation. The amount of CCD showed good relationship with the unwashed gum level of the gasoline. In general, smaller dosages produce less CCD. This means that detergents which have good IVD and PFID effectiveness at smaller dosage are better with regard to CCD. We analyzed the CCD by C13-NMR, GPC and IR method. The detergent contributes to CCD. Vehicle emissions tests were carried out to evaluate the effects of CCD on exhaust emissions.

In response to various reformulated gasoline regulations, several studies have been conducted to evaluate the relationship between fuel properties and vehicle exhaust emissions. These studies, however, have focused on the fuel effect and have not examined the most promising advanced technology emission control systems on low emission vehicles. Toyota's reformulated gasoline research first set out to study the effect fuel compositions has on 2 different emission control systems. On both systems, non-methane hydrocarbon (NMHC) emissions were significantly affected by the 50% and 90% distillation temperature (T50 and T90). A correlation was also found exhaust olefine content and the amount of MTBE contained in the fuel. Research was also conducted on the specific ozone reactivity (SOR) of exhaust hydrocarbons. Various fuels with similar specifications but blended from different feedstocks were evaluated.