The present disclosure describes a method including: receiving input data from a gas and oil separation plant (GOSP), wherein: one or more demulsifiers is being injected into an emulsion to achieve a separation, a plurality of flow rates of water and the one or more demulsifiers are being measured inside the GOSP, the input data comprises the plurality of flow rates as well as temperatures corresponding to the plurality of flow rates, and determining, for each of the one or more demulsifiers, efficiencies of the separation based on the flow rates measured at corresponding temperatures; grouping respective efficiencies of separation according to a set of temperature ranges; and generating, for at least one temperature range, a histogram for the at least one temperature range; ranking the one or more demulsifiers according to the histogram; and providing a feedback to indicate a ranked order of the one or more demulsifiers.