The mixing of different polyolefins, several calcium-based fillers, and a type of vegetable oil was investigated. The effect of viscosity and type of polyolefin on Young’s modulus, yield stress, and elongation at yield has been determined. Tensile and machine torque properties have been studied for both mixing at 180 degrees C and at 250 degrees C as a function of the content of several types of calcium carbonate or calcium hydroxide filler. The influence of the addition of a sunflower oil as a lubricant has also been characterized. SEM micrographs indicate some problems of the formation of agglomerates and the influence of particle size on matrix morphology and filler/matrix adhesion. Physical and chemical interactions among high-density polyethylene (HDPE), vegetable oil, and calcium hydroxide was noticed. Spectra from infrared spectroscopy illustrate the formation of structures similar to metallic soaps, which integrate well within HDPE. Compared to calcium carbonate, results reveal excellent possibilities for the use of calcium hydroxide as a filler for polyolefins.