This paper summarizes studies of storage stability of distillate fuels and gasolines. The effect of oxidation on gum solubility is shown, as is the effect of fuel type on the composition and properties of gums formed. Typical gum compositions from hydrocarbon fuels are presented. Fuel components were labelled with radioactive tracers to measure gum formation in 110F storage. Sulfur compounds, nitrogen compounds, and unsaturated hydrocarbons are the most reactive fuel components in gum formation. The effect of omitting single types of compounds from a 17 component synthetic mixture of pure compounds is discussed. A general equation for fuel deterioration is presented. A computer program is used to fit curves to storage data for simple mixtures, gasolines, and distillate fuels.
A test procedure and correlations were developed for predicting the amounts of gum and lead precipitate that will form in a gasoline during storage for periods up to 32 weeks at 110 F. The amounts of gum and lead precipitate formed in 24 commercial and military gasolines during a 16-hr oven test at 200 F were compared with the amounts formed in the same gasolines stored at 110 F and analyzed following 8-, 16-, and 32-week storage periods. A direct relationship was found between the amounts of lead precipitate formed during the oven test and those formed during long-term storage. The gum relationship, however, needed adjusting in proportion to the amount of oxygen consumed in the gum-forming reaction. The storage performance of gasoline at temperatures below 110 F for periods as long as 5 years can be estimated with a modified Arrhenius equation which is presented.