High Mileage Emission Deterioration Factors from Euro 6 Positive and Compression Ignition Vehicles

The current European fleet of vehicles is ageing and lifetime mileages are rising proportionally. Consequently, a substantial fraction of the vehicle fleet is currently operating at mileages well beyond current durability legislation (≤ 160,000 km). Emissions inventories and models show substantial increases in emissions with increasing mileage, but knowledge of the effect of emissions control system deterioration at very high mileages is sparse. Emissions testing has been conducted on matched pairs (or more) of diesel and gasoline (and CNG) vehicles, of low and high mileage, supplementing the results with in-house data, in order to explore high mileage emission deterioration factors (DF). The study isolated, as far as possible, the effect of emissions deterioration with mileage, by using nominally identical vehicle models and controlling other variables. Several emissions species were considered, including pollutants under consideration for control at Euro 7, with measurements made and data included from chassis dynamometer testing (WLTC and real driving emissions cycles) and from driving on the road using portable emissions measurement systems (PEMS). In addition to specific vehicle measurements, Remote Sensing Detection (RSD) data was used to help select vehicle pairs for testing, to interrogate Euro 5 single vehicle-model emissions deterioration across the full mileage spectrum for a historical perspective, and to evaluate pooled (similar) vehicle types for mileage-related emissions control deterioration. Data was analysed to identify emissions DF in two ways: firstly, to look at the differences between pairs at high and low mileages and secondly, to determine the deterioration gradient with mileage according to fuel type and test cycle. These deterioration gradients were cross validated against similar gradients determined from a large RSD database. Results showed increases in emissions control deterioration from 160,000km to 200,000km and further deterioration out to 240,000km for several pollutants; diesel DF were generally higher than gasoline DF for the same pollutants, and DF determined from RDE tended to be higher than DF determined from WLTC testing.