The stability of an oil-based fluid crude oil fluid may be determined by measuring a first RI value of the crude oil that does not comprise a solvent where the first RI value is used to determine a first solubility parameter therefrom. A second RI value may be taken from the crude oil at a point of asphaltene flocculation during a turbidimetric flocculation titration. The second RI value may be used to determine a second solubility parameter. A process for refining the crude oil may be controlled by maintaining the process or implementing a change to the process based on a ratio of the first solubility parameter to the second solubility parameter.