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Legislations worldwide have started imposing stringent emission standards for particulate matter (PM) emitted by diesel engines. The main reason for these actions is the adverse effects on human health caused by particle emissions. Conventional ceramic Diesel Particulate Filters (DPF) have proven exceptionally effective in reducing particulate emissions with efficiencies of 90% or more. However, these filters require regular active regenerations as well as periodical ash removal in order to avoid a blockage of the exhaust line. These procedures are both costly and complex and as a result alternative aftertreatment solutions have been developed. One of these solutions is the Particle Oxidation Catalyst, POC-X. The main aim of the POC-X is not to equal the high efficiencies of the DPF, but to achieve the best possible particle reduction without creating the risk of blocking or the need for complex filter regeneration procedures.

With the increased use of engines utilizing direct fuel injection and the upcoming introduction of more stringent emissions legislation that regulates not only particulate mass (PM) but also particulate number (PN), the emissions from Direct Injection Spark Ignition Engines (DISI) are an increasing concern. Gasoline Particle Filters (GPF) represent a potential way to reduce particle number emissions from DISI engines and are particularly effective considering the tough performance requirements during cold start and over RDE operation. Even though some learning from the development and application of particulate filters to diesel engines can be transferred to gasoline engines, the particle composition, mass to number ratio as well as the exhaust gas temperature and composition from gasoline engines are significantly different to diesel engines. Therefore, there is the need to study the application of particulate filters to gasoline engines in more depth.

This study presents the impact of two engine oil additives on fuel efficiency and CO2 emissions. Formulations containing either Olefin Copolymer (OCP) or Comb polymer (Comb) were compared in tests for fuel efficiency retention, fine particle emissions, and ash accumulation in the gasoline particulate filter. The Comb formulations showed higher fuel efficiency throughout the testing, retaining this efficiency after three distinct engine aging test cycles. No significant differences between formulations were observed in oil consumption, ash accumulation, and filtration efficiency.