A Study into the Impact of Engine Oil on Gasoline Particulate Filter Performance through a Real-World Fleet Test 2019-01-0299

Increasingly stringent vehicle emissions legislation is being introduced throughout the world, regulating the allowed levels of particulate matter emitted from vehicle tailpipes. The regulation may prove challenging for gasoline vehicles equipped with modern gasoline direct injection (GDI) technology, owing to their increased levels of particulate matter production. It is expected that gasoline particulate filters (GPFs) will soon be fitted to most vehicles sold in China and Europe, allowing for carbonaceous particulate matter to be effectively captured. However, GPFs will also capture and accumulate non-combustible inorganic ash within them, mainly derived from engine oil. Studies exist to demonstrate the impact of such ash on GPF and vehicle performance, but these commonly make use of accelerated ash loading methods, which themselves introduce significant variation. Through a nine-vehicle real-world field trial in Shanghai, China, this study seeks to understand the impact of engine oil ash level on GPF ash capturing, and the subsequent impact of GPF pressure-drop associated with ash collection. Briefly, it is shown that an engine oil’s ash level directly impacts the amount of ash collected within GPF, with higher ash engine oils resulting in increased ash accumulation. Collected ash within the GPF acts to reduce both the mass and number of emitted particulate matter, by itself acting as a filter membrane. The specific engine oil ash level does not impact this. Furthermore, ash within the GPF has the undesirable impact of increasing exhaust backpressure, the extent of which is determined by the amount of ash captured. As such, the use of lower ash engine oils minimizes exhaust backpressure increase associated with GPF ash collection over a vehicle’s lifetime.