Previous research indicates that the low temperature combustion (LTC) is capable of producing ultra-low nitrogen oxides (NOx) and soot emissions. The LTC in diesel engines can be enabled by the use of heavy exhaust gas recirculation (EGR) at moderate engine loads. However, when operating at higher engine loads, elevated demands of both intake boost and EGR levels to ensure ultra-low emissions make engine controllability a challenging task. In this work, a multifuel combustion strategy is implemented to improve the emission performance and engine controllability at higher engine loads. The port fueling of ethanol is ignited by the direct injection of diesel fuel. The ethanol impacts on the engine emissions, ignition delay, heat-release shaping, and cylinder-charge cooling have been empirically analyzed with the sweeps of different ethanol-to-diesel ratios. Zero-dimensional phenomenological engine cycle simulations have been conducted to supplement the empirical work. The multifuel combustion of ethanol and diesel produces lower emissions of NOx and soot while maintaining the engine efficiency. The experimental setup and study cases are described, and the potential for the application of an ethanol-to-diesel multifuel system at higher loads has been proposed and discussed.