The existence of deposits in the combustion chamber will affect the performance and emissions of the engine, and this will not be avoided using petroleum fuels and lubricating oils. This makes it necessary to study the formation, composition, structure and influential factors of the deposit, which will provide a basis for reducing deposit on the engine. This article reviews experimental studies on the formation of deposits in engine combustion chambers, as an effect of the use of a mixture of biodiesel on diesel fuel, with an emphasis on the composition of deposits, the influence of temperature, and study methods. This study is based on a report by researchers who conducted various experiments with various types of biodiesel and various methods to obtain deposit formation characteristics in mixing biodiesel. The study of deposit formation with several types of newly developed fuels was also included. The mechanism of deposit structure analysis in various ways is also explained. Based on the results of the study, it shows that deposits can be formed or can be determined depending on the nature of the fuel. Furthermore, about the deposit research approach to its chemical composition and physical structure is taken. Finally, regarding the formation of deposits in diesel engines, the composition of deposits and factors that influence deposit formation, such as engine type, fuel type, are mentioned through experimental studies on machines.