In modern internal combustion engines, fuel is injected into the cylinders and is burnt to produce power. The splashing of fuel drops as they impact the piston directly affects engine efficiency and pollutant emission. Due to the small drop size and high impact velocity, diesel fuel drop impingement is difficult to study experimentally. Therefore, we use high resolution CFD simulations to investigate the splashing phenomenon. The results of such simulations can be used to develop refined spray-wall interaction models for diesel engine conditions. Such models will enhance the accuracy of engine simulations in terms of engine efficiency and pollutant emission, providing engine manufacturers with the tools necessary to design cleaner more fuel efficient diesel engines.