Gasoline can oxidize during storage giving rise to formation of gums, which cause deposit formation in the intake system of engines, affecting the performance, derivability and emissions characteristics of the vehicles. To evaluate the deposit-forming tendency of gasoline, a small-scale engine test method using a modern technology gasoline engine, was developed and reported in SAE paper
2001-28-0039. Further work has been done in this area to demonstrate the ability of the test method to distinguish between different quality of fuels. Data on the performance of different base fuels and various commercial deposit control additives, with regard to their effect on the deposit forming propensity and cleanliness characteristics, in the engine combustion chamber and intake systems is reported. In order to investigate the effect of prolonged storage of gasoline on deposit forming tendency tests were conducted with base fuel samples stored over a period of two years. Results of the tests show that during prolonged storage, lighter fractions of olefins evaporates and remaining gasoline oxidizes giving rise to the formation of gums and gum precursors that can increase the deposit forming tendency.