Thermal and Rheological Behavior of the Organogelators 12-Hydroxystearic Acid and Its Calcium Salt

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12-Hydroxystearic acid (12-HSA) is widely used as a low-molar-mass organogelator (LMOG), especially in the field of lubricants. This study aims to compare the effectiveness of a technical grade of 12-HSA and its calcium salt (12-HSCa) as a gelling agent for different commercial oils. Their partial or full melting is required for the crystallization into fibers to occur upon cooling. The organogels were mainly investigated using rheological and DSC measurements. In agreement with the literature, low concentrations (<2 wt %) of pure or technical grade 12-HSA allowed us to obtain strong organogels with negligible thixotropic behavior. The oil gelation process is very simple and robust and is achieved by heating the oil above the melting temperature of 12-HSA to complete dissolution and then cooling to ambient temperature. 12-HSCa was less efficient as an organogelator than its fatty acid, requiring much higher concentrations (>15 wt %) to obtain organogels. Moreover, it exhibited a peculiar behavior requiring a very specific temperature cycle for gel preparation. This was explained by the polymorphism of 12-HSCa, leading to different dissolution–precipitation and growth kinetics. The impact of the addition of common surfactants in lubricant formulations and the nature of the oils were studied. This information is particularly relevant to the manufacture of greases and lubricants. Both LMOGs effectiveness decreased in the presence of a surfactant or by increasing the degree of oil refinement due to a lower content of polar heteroaromatic components.