In recent years, rubber manufacturers have turned to modulating thermal and electrical conductivity of fillers for improved performance. Formulation development for improved performance is difficult without using thermal conductivity, dynamic mechanical properties, and electrical conductivity to understand the mechanisms governing performance. This study examines three fillers to better understand their effects on thermal conductivity, mechanical properties (Payne effect), and electrical conductivity. The fillers were N326, conductive black (XC-72), and metal oxide (TiO2). The filler type and structure had significant effects on the properties. The effect of thermal conductivity on the uniformity was examined. The state of cure from inside to outside of thick rubber parts was measured by modulus profiling.