Fuel efficiency and emission performance sensitivity to fuel reactivity was examined using Delphi’s second-generation Gasoline Direct-Injection Compression Ignition (Gen 2.0 GDCI) multi-cylinder engine. The study was designed to compare a US market gasoline (RON 92 E10) to a higher reactivity gasoline (RON 80) at four operating conditions ranging from light load of 800 rpm / 2.0 bar gross indicated-mean-effective pressure (IMEPg) to medium load of 2000 rpm / 10.0 bar IMEPg. The experimental assessment indicated that both gasolines could achieve good performance and Tier 3 emission targets at each of the four operating conditions. Relative to the RON 92 E10 gasoline, better fuel consumption and engine-out emissions performance was achieved when using RON 80 gasoline; consistent with our previously reported single-cylinder engine research .More specifically, a fuel consumption improvement was observed at the low load operating conditions (800 rpm / 2.0 bar IMEPg and 2000 rpm / 2.6 bar IMEPg) when using the RON 80 gasoline, compared to using market RON 92 E10 gasoline mainly due to better combustion stability that is directly associated with the fuel’s higher reactivity. For mid-load operation (1500 rpm / 6.0 bar IMEPg and 2000 rpm / 10.0 bar IMEPg), significantly lower fuel consumption was achieved when using the higher reactivity (RON 80) gasoline due to significantly lower boost pressure requirements and an enhanced combustion process. Clear differences in low temperature heat release (LTHR) behavior for this partially premixed compression ignition (PPCI) combustion process was also observed between the two gasolines.Specifically for the Delphi Gen 2.0 GDCI multi-cylinder engine, fuel consumption and engine-out emission targets were able to achieve when using both current market RON 92 E10 gasoline and a higher reactivity RON 80 gasoline. Furthermore, the higher reactivity RON 80 gasoline exhibited further improvement of light-to-medium load performance and emissions.