The development of magnesium (Mg) alloys capable of operating at the demanding working temperature of above 200 °C and the ability of using high pressure die casting for high-volume manufacturing are the most advanced development in manufacturing critical parts for internal combustion (IC) engines used in power tools. Here we introduce the development of a Mg-RE based die-cast Mg alloy for elevated applications in small IC engines. The developed Mg-RE based die-cast Mg alloy shows good ambient and high temperature strength, and it also has excellent high temperature creep resistance. In addition, the developed Mg-RE based die-cast Mg alloy shows good stiffness at elevated temperatures. Furthermore, the developed Mg-RE based die-cast Mg alloy exhibits good thermal conductivity at ambient and high temperatures, which is a key point that is normally neglected during the development of high temperature Mg alloys.