The concept of cluster nozzles, grouping multiple smaller holes together has the potential to improve mixing in the center of the spray and therefore presents an opportunity to lower the production of soot. This concept is characterized by a high number of degrees of freedom concerning the spray orientation, number of spray holes, and configurations of placement of holes in a group. The intention behind the cluster nozzles is to provide a better primary breakup and therefore a better mixture formation caused by the smaller nozzle holes while keeping a comparable penetration length of the vapor phase due to merging of the sprays. Ten cluster nozzles were tested in a single-cylinder engine and compared with a conventional nozzle. Clusters are generally regarded as better than conventional nozzles for partial-load operation. While the results confirm the above notion, they also show some cluster configurations to improve upon the conventional nozzles in high-load conditions. The results show that apart from the orifice size or number in a group, the spatial orientation of the spray is also a critical factor for application in diesel engines. These findings could be helpful for conceptualizing cluster nozzles for applications in the whole operating range of a diesel engine.