Various unleaded gasoline formulations and gasoline components obtained from refinery streams were evaluated for their deposit forming tendencies in several multicylinder automotive engines. A pair of GM 2.0L engines equipped with throttle body fuel injection and a GM 1.8L equipped with an electronic feedback carburetor were utilized to determine fuel property effects on intake valves, cylinder head, and piston top deposits. Engine performance with respect to octane requirement increase was measured.Various analytical techniques were used to study a variety of fuel properties. Analyses of gasoline formulations and related fuel components such as light reformate, motor alkylate, benzene raffinate, and light catalytically cracked refinery streams were accomplished. Gas chromatography-mass spectrometry (GC/MS) and flourescence indicator absorbance (FIA) analysis were performed on these fuels to determine their composition. Categorical and specific characterization of the constituents of these fuels were examined so that evaluations could be made relating the fuel or component to its engine performance or deposit forming tendency.