Polar heteroatomic species have been correlated with storage instability problems in both petroleum and shale derived middle distillate fuels. Instability is defined as the formation of filterable sediments and fuel insoluble gums. Heteroatoms (oxygen, nitrogen and sulfur) have been found to be greatly enhanced in such sediments. Trace levels of certain organo-sulfur compounds, especially sulfonic acids, have been found to significantly alter the deposit formation process. Hydroperoxides have also been implicated in the instability process which would point to free radical mechanisms. The effectiveness of organic amines as additives suggests that acid-base chemistry is also involved in the formation of deposits. This paper reports on a study of organo-sulfur, nitrogen and hydroperoxide compounds employed as dopants in fuels. The most detrimental dopant species were sulfonic acids.