Gasoline versus diesel: Comparing CO2 emission levels of a modern medium size car model under laboratory and on-road testing conditions
For this paper, the CO2 emissions levels of two versions of the Volkswagen Golf, one diesel (Golf TDI) and one gasoline (Golf TSI), were compared both in laboratory tests and in on-road measurements under real-world driving conditions. Both vehicles were Euro 6 type approved prior to the introduction of the Worldwide Harmonized Light Vehicles Test Procedure (WLTP) and Real Driving Emissions (RDE) NOx not-to-exceed limits in the EU.
For all tests performed under laboratory conditions, the gasoline-powered Golf TSI showed lower CO2 emissions than the comparable diesel-powered Golf TDI. At lower ambient temperatures, the CO2 emissions were higher for both vehicles.
Also during the real-world driving tests, lower CO2 emissions were measured for the Golf TSI. A subsequent driving dynamicity analysis suggests that both vehicles, when driven in the same manner at the same ambient conditions, have similar real-world CO2 emissions, with a slight benefit for the Golf TSI. These findings are also supported by the CO2 emission values reported by consumers.
A comparison of the current gasoline and diesel VW Golf models with similar C-segment vehicle models of other manufacturers revealed that the CO2 emissions of the Golf TDI are in the same range as the diesel models of other manufacturers. It also shows that the CO2 emissions of the Golf TSI are notably lower than the emissions of all other compared vehicles. This implies that a considerable CO2 emission reduction can be achieved for other gasoline powered C-segment vehicles as well.
The results of this vehicle testing project show that at least for the popular C-segment, a modern gasoline vehicle can have the same or even lower CO2 emissions than a comparable diesel version at a considerably lower price. This finding holds true not only for laboratory testing but also for on-road measurements under real-world driving conditions.