Rapid penetration of diesel engines is expected in North America because of their better fuel efficiency and lower greenhouse gas (GHG) emissions. Diesel engine components, particularly cylinder heads, are made of cast irons and replacing them with aluminium alloys could result in a significant weight reduction and consequently better fuel efficiency. Aluminum alloys for diesel engine applications need to withstand higher operating temperatures and pressures as compared to conventional 3xxx based alloys that lose strength above 150oC. This paper presents selected results pertaining to alloy development with improved high temperature performance based on the modified 356 composition. Such alloys with engineered chemical composition and properly designed heat treatment could have improved properties at temperatures up to 250oC. The advanced thermal analysis techniques including dilatometer analysis were used to determine the effect of alloying additions on thermal characteristics including aging kinetics and its impact on casting service performance. Selected structure analysis results including XRD and TEM/EDX as well as elevated temperature tensile testing are presented.