An experimental study was conducted on a single cylinder gasoline compression ignition (GCI) engine for gasoline-biodiesel (GB) blends from 5 to 20% by volume with varying starts of injection (SOI). In particular, the aim was to examine the combustion phenomena and exhaust emissions of the engine for the various SOI and chosen GB blends compared with neat diesel fuel. The engine was running with 1200 rpm, 70 MPa of injection pressure, 800 mu s of injection duration and various SOI from early injection timing (before top dead center (BTDC) 75 degrees CA) to around top dead center (TDC) BTDC 18 degrees CA. The results showed that the earlier the SOI of GB blends, the shorter the ignition delay compared to diesel fuel. Besides, the GB blends resulted in almost the same combustion duration as diesel fuel both for earlier and later SOI. The coefficient of variability (COV) of IMEP GB blends (under 3%) for every SOI is clear evidence of combustion stability. Furthermore, the thermal efficiency for GB blends was found to be almost equivalent with diesel fuel for all conditions. In the case of emission, GB blends produce lower HC compared to diesel, as expected, because of their homogeneous mixing capabilities. However, a higher NOx emission from GB blends was observed, which might be a result of excess oxygen in the fuel. (C) 2016 Elsevier Ltd. All rights reserved.