One of the major causes of premature failure in A319 aluminum alloy powertrain components is the accumulation of thermal stresses. Consequently, the engine operating temperature is restricted to prevent large internal temperature gradients in the components, thereby reducing thermal efficiency. The objective of this research was to investigate the influence of solidification parameters on the thermal conductivity of A319 alloy, in an effort to promote uniform temperature distributions in powertrain components. Castings with varying mould preheating temperatures were characterized using thermal analysis, microstructural analysis, mechanical testing, and thermal conductivity measurements via the transient plane source method. The results indicated that increasing solidification rate was associated with two competing phenomena: Whereas finer secondary phases improved conductivity, a finer dendritic structure reduced conductivity. As a result, a critical solidification rate was found to attain maximum thermal conductivity in A319.