Polar heterocyclic compounds present in middle distillate fuels have been implicated in the chemical processes involved in fuel instability. Nitrogen-containing aromatics (e.g., pyrroles, pyridines, quinolines, indoles) are often intimately involved in the reactions leading to deposition of insoluble sediments and gums in both petroleum and shale derived fuels (1, 2). Although results of fuel dopant studies are useful in screening potentially active compounds, the results must be taken with caution (3, 4). For example, the particular accelerated (i.e., high temperature) stress regimen employed may have a variable effect upon the results obtained. Additionally, interactive effects between labile species need to be assessed in greater detail (2,4).