Syngas, also known as producer gas or wood gas, is a gaseous biofuel produced by gasification of biomass. It is mainly composed of hydrogen and carbon monoxide with a smaller share of methane, all diluted by nitrogen and carbon dioxide. Despite having carbon in its composition, since it is made from biomass, it is considered low to zero-carbon and being so makes it one candidate for reducing carbon emissions of internal combustion engines. This work focuses on the effect of different syngas compositions on the performance and the exhaust emissions of compression ignition engine with decane pilot injection as a diesel surrogate. Results showed that thermal efficiencies over 39% are possible with a variety of syngas with less than 10% energy contribution of decane. NO x and soot emissions were generally lowered by increasing the syngas/decane ratio, whereas CO and Total HC emissions increased. Additionally, relations between engine performance/emissions and fundamental properties of varying Syngas compositions were established. Further investigation on other combustion properties, such as stretch sensitivity of the syngas/air flame, are needed in order to better predict optimum operability.