Natural gas is one of the most promising alternative fuels to meet the new stringent Euro 6 emissions regulations in the European Union, as well as the planned CO2 emissions reductions. For spark-ignition (SI) engines, bi-fuel fuelling equipment is widely available and engine conversion technology for European automobiles is well established, thereby facilitating usage of CNG in this engine type. This study investigates the implications of natural gas fuelling of a passenger car featuring a spark-ignition engine regarding the possibility of meeting Euro 6 emissions limits for gaseous pollutants. This paper presents an analysis of CO, THC, NMHC, NOx and CO2 emissions during testing of a vehicle on a chassis dynamometer, fuelled with CNG, in the context of the new Euro 6 emissions requirements. The analyses were performed on a Euro 5 bi-fuel vehicles with an SI engine equipped with an MPI feeding system operating in closed-loop control, a typical three-way-catalyst, and a heated oxygen sensor. The vehicles had been adapted by their manufacturer for fuelling with CNG by using additional special equipment mounted onto the existing petrol fuelling system. The vehicles tested featured a multipoint gas injection system latest generation. The tests subject to the analyses presented here were performed in the Engine Research Department of BOSMAL Automotive Research and Development Institute Ltd in Bielsko-Biala, Poland, within a research programme investigating the influence of alternative fuels on exhaust emissions from automotive vehicles with spark-ignition and compression-ignition engines.