<div class="section abstract"><div class="htmlview paragraph">Gasoline Direct Injection Compression Ignition (GDCI) is a partially premixed low temperature combustion process that has demonstrated high fuel efficiency with full engine load range capabilities, while emitting very low levels of particulate matter (PM) and oxides of nitrogen (NO_x). In the current work, a comparison of engine combustion, performance, and emissions has been made among E10 gasoline and several full-boiling range naphtha fuels on a Gen 2 single-cylinder GDCI engine with compression ratio of 15:1. Initial results with naphtha demonstrated improved combustion and efficiency at low loads. With naphtha fuel, hydrocarbon and carbon monoxide emissions were generally reduced at low loads but tended to be higher at mid-loads despite the increased fuel reactivity. At higher loads, naphtha required less boost pressure compared to gasoline, however, up to 20% additional EGR was required to maintain combustion phasing. The higher reactivity of naphtha did cause some reduction of peak load for the operating strategy tested, when constrained to the targets used in this study. For all fuels, particle size distributions were bimodal and had similar numbers of particles larger than 40 nm, while there were some differences in numbers of smaller particles. Based on an efficiency loss analysis, the fuels exhibited generally similar performance over the load range.</div></div>