A petroleum-based fluid sample may be centrifuged in a centrifuge vial where a light may be passed through the petroleum-based fluid sample to identify an amount of transmitted light at two or more time intervals. The stability of the foulant(s) and/or efficacy of the foulant inhibitors to prevent the destabilization of the foulants may be determined by comparing a change in the amounts of transmitted light through the petroleum-based fluid sample. The petroleum-based fluid sample may include a petroleum-based fluid, at least one foulant, and an optional additive for destabilizing the foulant(s). The additive may be or include a first component, such as but not limited to n-alkanes, iso-alkanes, alkenes, alkynes, cyclo-alkanes, natural gas, natural gas condensate, alcohols, ethers, ketones, organic acids, acetates, carbon dioxide, and combinations thereof.