The present invention provides an aluminum casting alloy with a composition including 4%-9% Si; 0.1%-0.7% Mg; less than or equal to 5% Zn; less than 0.15% Fe; less than 4% Cu; less than 0.3% Mn; less than 0.05% B; less than 0.15% Ti; and the remainder consisting essentially of aluminum. The inventive AlSiMg composition provides increased mechanical properties (Tensile Yield Strength and Ultimate Tensile Strength) in comparison to similiarly prepared E357 alloy at room temperature and high temperature. The present invention also includes a shaped casting formed from the inventive composition and a method of forming a shaped casting from the inventive composition.