A catalyzing factor for the continuous search to optimize the compression ignition engines is the impact it has on the environment. The compression ignition engines find applications in the transportation sector, agriculture, energy, and construction sectors, and the optimization of its performance will thus not be an effort in futility. Many studies have focused on the optimization of the performance of compression ignition engines. The ones of interest reviewed herein can be broadly categorized as combustion chamber geometry studies, fuel studies, and process types studies. The combustion chamber geometry poses an impact on the in-cylinder fluid motion. This influences the combustion process which in-turn affects the engine performance and emission characteristics. The fuel type is also an influencer of the engine performance and emission characteristics drawing its impact from its properties. The process type also poses an impact on the combustion process and can influence the engine performance and its emission characteristics.