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A study was performed to quantify the impact of blending Fatty Acid Methyl Ester (FAME) with Gas-to-Liquids (GTL) diesel fuel on engine exhaust emissions. Fuels that were considered in the study included blends of GTL and EN590 diesel containing 0, 7, and 20 volume % of Soy and Rapeseed Methyl Ester (SME and RME). Part of the study focused on European engine technology, and tests were performed on a Euro 3 passenger car engine and a Euro V heavy-duty engine. A limited study was performed using a heavy-duty engine meeting the US 2004 emission standards, in which case comparisons between the GTL diesel and FAME blends were made with US 2D and California Air Resources Board (CARB) reference fuels. The results showed particulate mass (PM) reductions to varying degrees with all of the GTL/FAME blends.

Light-duty diesel vehicles that make use of a diesel particulate filter (DPF) generally require periodic active regenerations. This is achieved by late, in-cylinder post-injections designed to add unburned fuel into the exhaust system to raise the DPF temperature and burn off the soot. These late injections do not atomise and evaporate as readily as during normal combustion causing a portion of this fuel to impinge on the cylinder wall and wash down, with the engine oil, into the sump. This can result in degradation of the engine oil which could lead to increased engine wear and/or engine failure. When investigating which fuel properties have an effect on oil dilution, most literature suggests high final boiling point fuels increase fuel addition rates to engine oil.