Diesel fuel may be blended with ethanol as a bio-fuel extender. However, ethanol is not miscible with diesel fuel, so an emulsifier must be added to a diesel-ethanol blend to prevent the ethanol fraction from separating in a fuel tank. This diesel-ethanol blending and storage problem can be avoided by installing a separate ethanol fuel tank, fuel pump, and ethanol fuel injector that operate in parallel with the standard diesel fuel injection system.A Medium Duty diesel truck has been modified for blending ethanol with the standard diesel fuel consumed by the engine. The ethanol is injected into the intake air so that diesel and ethanol aerosols are blended in the engine cylinder. The ethanol injection is synchronized with the diesel fuel injection, where the proportion of ethanol to diesel fuel is constant.Vehicle tests include EPA FTP procedures on a chassis test cell dynamometer. Exhaust emissions are quantified with a Portable Emission Measurement System (PEMS) that measures both pollutants and particulate matter (PM). The results show a 10% to 20% reduction in fuel consumption and particulate emissions when 8% ethanol is added to diesel fuel.