This invention relates to a process for determining the fouling tendency of a crude petroleum oil feed, comprising the steps of:(a) mixing a selected volume of crude petroleum oil sample with a selected volume of a solvent medium,(b) agitating the resulting mixture to solubilize fouling-determining materials in the solvent medium,(c) removing a sample of the resulting solvent medium,(d) determining absorbance of the resulting solvent medium at 230-270 nm and subtracting from the absorbance that of control solvent medium to obtain corrected absorbance of the resulting solvent medium and(e) determining the fouling tendency of the crude petroleum oil sample by correlating the corrected absorbance of the resulting solvent medium with calibration data specific for the solvent medium used, the ratio of oil sample to polar solvent and the wavelength at which absorbance is determined.The thus-determined fouling tendency can be used to predict the amount of antifouling agent, required to prevent fouling during downstream processing.