The internal combustion (IC) engine is one the greatest inventions since the industrial revolution. The computer marked the advent of the informational revolution. The use of computer models in IC engine design and optimization has significantly improved engine efficiency and reduced engine pollutant emissions over the past decades. In the foreseeable future, computer-aided engine optimization will continue to strengthen the vitality and the role of IC engines in modern transportation. The present chapter reviews the important role of IC engines and the challenges that IC engines are facing in terms of sustainability, and their impact on the environment is emphasized. We also briefly summarize the current status of engine modeling and review recent progress on computational optimization of IC engines in this chapter.