The introduction of fatty acid methyl ester (FAME) into the diesel pool has led to an increase in the incidence of diesel fuel filter blocking. In contrast to conventional diesel, filter blocking events can occur above a fuel's Cloud Point (CP). It has been shown that this phenomenon is due to trace levels of impurities carried over from the original oil source into the final fuel. The two species identified as being the main cause of the filtration problems are saturated monoglycerides (sMG) and sterol glucosides (SG).Reported in this paper is an extensive study completed to understand the impact that these impurities have on the filterability of FAME and FAME containing fuels. This has been investigated using laboratory based filterability tests that incorporate a specific cold soak and the critical contaminant levels causing failure have been determined. In addition to this, the appearance of the crystals formed and their coverage of the fuel filter surface have been studied using scanning electron microscopy (SEM).These two techniques have also been used to identify and select additive technology that can positively impact filterability when sMG and SG precipitate from either FAME or fossil fuel containing a portion of FAME.