Engine Tests and Analysis Examine Chemical Relationships for Self-Ignitability of Ethanol and Gasoline: As gasoline is blended with ethanol at higher fractions to reduce exhaust emissions and petroleum fuel consumption, a gasoline engine designed to operate on premix compression ignition (PCI) combustion may have combustion problems because ethanol ignition characteristics are different from those of gasoline. Researchers at Suzuki Motors and Waseda University investigated the ignition characteristics of ethanol and iso-octane in detail through engine tests and analysis. A 0.33-liter, single-cylinder, spark-ignition engine was operated on ethanol and gasoline injected by two separated fuel injection nozzles. The compression ratio was increased to 15 to enable PCI combustion with greater valve overlap. This chapter reports the results of both engine tests and analyses and discusses the chemical reactions that lead to research conclusions.