A literature review was conducted and fuel survey data were obtained to identify the use of metallic fuel additives (MFAs) within market fuels and determine their effects on engines, exhaust systems, and vehicle performance. The primary focus was on modern vehicles equipped with on-board diagnostic (OBD) systems and advanced emissions control systems. For gasoline, this includes vehicles categorized as National Low Emission Vehicles (NLEV) and Tier 2 or beyond in the U.S., and Euro-3 through Euro-6 in the EU. For diesel, this includes engines/vehicles with original equipment manufacturer (OEM)-equipped oxidation catalysts and diesel particulate filters.
The literature search of peer-reviewed papers and other publicly available articles returned over 100 items relevant to the use of organometallic fuel additives, but did not provide significant evidence of widespread use of MFAs in either gasoline or diesel fuels. It is possible, however, that in specific cases, MFAs are added to fuels downstream of refinery blending. Recent fuel survey information confirmed that relatively few MFAs are found in market fuels, and they are generally present at quite low concentrations. Manganese was found most frequently, at concentrations as high as 66 mg Mn/L. Iron was detected less frequently and at lower levels, typically at concentrations ranging from 5 to 25 mg Fe/L. Silicon and other contaminants were frequently seen, albeit at very low levels. Evidence suggests that both manganese and iron, as well as other MFAs that are less frequently used, can contribute to deposits in combustion chambers and on exhaust components, resulting in poor performance and increased vehicle emissions. Although not in widespread use, the most common application of MFAs involves regeneration of diesel particulate filters (DPF). However, this is considered an aftermarket treatment, as the MFAs are not blended directly into marketplace diesel fuels.
