Depletion of fossil fuel reserves, the unsteadiness of their prices and the increasingly stricter exhaust emission legislation put forward attention of world towards use of alternate fuels. The ever increasing demand for ecologically friendly vehicles can be met by use of clean fuels like Compressed Natural Gas (CNG) and Hydrogen (H2). Lower carbon to hydrogen ratio of CNG makes it a cleaner fuel, due to this CNG is gaining popularity as an internal combustion (IC) engine fuel in transport sector. Hydrogen fuel for IC engines is also being considered as a future fuel due to its simple carbon less structure. However, several obstacles have to be overcome before widespread utilization of hydrogen as an IC engine fuel can occur in the transport sector. The 18 percent hydrogen enriched CNG fuel referred to as HCNG has the potential to lower emissions and could be considered a first step towards promotion of a Hydrogen economy.This paper presents the optimization strategy for HCNG on 6-cylinder sequential gas injection based heavy duty CNG engine. The six cylinder engine was chosen due to its importance for urban bus transportation. The engine was optimized for HCNG fuel by varying the ignition timing, injection duration and varying the air-to-fuel ratio. During optimization with HCNG, ignition timing was retarded to avoid knocking as Hydrogen is fast burning fuel. Initial performance of the engine on HCNG was compared vis-à-vis CNG and, thereafter, the engine was subjected to endurance test as per BIS 10000 norms for 100 hours with HCNG. Performance of the engine was monitored at 10 hour intervals and at the end of the endurance cycle performance of the engine was assessed as per European Transient Cycle (ETC) with emission measurements.Experimental investigations with HCNG shows reduction of CO, THC, CH4 and CO2 emissions and NOx increased as compared to CNG. The average work was reduced with HCNG while at the end of the endurance test, the work showed increase. Further, the results after the endurance test of 100 hrs showed increase in CO, THC and CH4 emission whereas NOx and CO2 emissions reduced. All emissions were found to be much lower than the Euro IV emission norms for the heavy duty engines and there were no significant changes in the CO2 values. Test results indicate that there were no significant changes observed in engine power output and specific fuel consumption (SFC) at the end of the endurance test. It can be concluded from the study that the HCNG could be a promising alternative fuel for meeting future energy needs with emissions reduction for transport and power generation.