Low temperature combustion (LTC) engine technologies are being investigated for high efficiency and low emissions. However, such engine technologies often produce high hydrocarbon (HC) and carbon monoxide (CO) emissions, and their operating range is limited primarily by the fuel properties. High reactivity gasoline fuels have been reported to help achieve partially premixed compression ignition (PPCI) at light-to-medium load conditions. In this study, two different fuels, a US market gasoline containing 10% ethanol (RON91 E10) and a high reactivity gasoline (RON80), were compared on a Delphi’s second generation Gasoline Direct-Injection Compression Ignition (GDCI) multi-cylinder engine. The engine was evaluated at three operating points ranging from a light load condition (800 rpm/2 bar IMEP) to a medium load condition (1500 rpm/6 bar IMEP and 2000 rpm/10 bar IMEP). The engine was equipped with two oxidation catalysts with exhaust gas recirculation (EGR) inlet located in-between. Samples were taken at engine-out, between the catalysts, and tailpipe locations to assess the engine-out and EGR inlet feed conditions, and the oxidation catalyst performance. In addition to raw exhaust emission measurement, part of the raw exhaust was diluted and sampled for HC speciation. Canisters were collected for volatile HCs, and novel sorbent membranes were used to collect semi-volatile HCs. Di-nitrophenyl hydrazine (DNPH) cartridges were used for collecting oxygenated species, such as aldehydes and ketones. Results showed overall lower HC emissions with the RON80 fuel compared to the RON91 E10 fuel. For both fuels, the percentage of aromatic HCs was higher in the exhaust than in the fuels themselves. High aldehyde and ketone engine-out emissions were observed for both fuels, indicative of the partial oxidation processes common in PPCI operation. The reported HC speciation information can be useful for the development of a robust emission control system.