Diesel-ignited gasoline and diesel-ignited methane dual fuel combustion experiments were performed in a single-cylinder research engine (SCRE), outfitted with a common-rail diesel injection system and a stand-alone engine controller. Gasoline was injected in the intake port using a portuel injector, whereas methane was fumigated into the intake manifold. The engine was operated at a constant speed of 1500 rev/min, a constant load of 5.2 bar IMEP, and a constant gasoline/methane energy substitution of 80%. Parameters such as diesel injection timing (SOI), diesel injection pressure, and boost pressure were varied to quantify their impact on engine performance and engineout ISNOx, ISHC, ISCO, and smoke emissions. The change in combustion process from heterogeneous combustion to HCCI like combustion was also observed.