Real world CO2 and NOx emissions from 149 Euro 5 and 6 diesel, gasoline and hybrid passenger cars

Abstract

In this study CO₂ and NO_x emissions from 149 Euro 5 and 6 diesel, gasoline and hybrid passenger cars were compared using a Portable Emissions Measurement System (PEMS). The models sampled accounted for 56% of all passenger cars sold in Europe in 2016. We found gasoline vehicles had CO₂ emissions 13-66% higher than diesel. During urban driving, the average CO₂ emission factor was 210.5 (sd. 47) gkm^-1 for gasoline and 170.2 (sd. 34) gkm^-1 for diesel. Half the gasoline vehicles tested were Gasoline Direct Injection (GDI). Euro 6 GDI engines <1.4ℓ delivered ~17% CO₂ reduction compared to Port Fuel Injection (PFI). Gasoline vehicles delivered an 86-96% reduction in NO_x emissions compared to diesel cars. The average urban NO_x emission from Euro 6 diesel vehicles 0.44 (sd. 0.44) gkm^-1 was 11 times higher than for gasoline 0.04 (sd. 0.04) gkm^-1. We also analysed two gasoline-electric hybrids which out-performed both gasoline and diesel for NO_x and CO₂. We conclude action is required to mitigate the public health risk created by excessive NO_x emissions from modern diesel vehicles. Replacing diesel with gasoline would incur a substantial CO₂ penalty, however greater uptake of hybrid vehicles would likely reduce both CO₂ and NO_x emissions. Discrimination of vehicles on the basis of Euro standard is arbitrary and incentives should promote vehicles with the lowest real-world emissions of both NO_x and CO₂.

Keywords: CO(2); GDI; NO(x); PEMS; Passenger cars; Real-world emissions.