Engine Tests Examine Contributions of Boiling Point and Viscosity in Deposit Formation: Biodiesel fuel tends to produce carbon deposits in the combustion chamber of a diesel engine operating on biodiesel fuel. Carbon deposits worsen engine performance and exhaust emissions and possibly cause piston rings to stick in the groove. Researchers at Ibaraki University, New Advanced Combustion Engineering (NACE), and the National Traffic Safety and Environment Laboratory (NTSEL) investigated production characteristics of carbon deposits in a 0.638-liter DI diesel engine operating on rapeseed methyl ester (RME) and diesel fuel blended with 5-percent RME (B5). In addition, RME was blended with dimethyl ether (DME) to reduce its viscosity and both carbon deposits on a fuel injection nozzle and smoke emission were evaluated during a 30-hour test. The chapter consists of 7 pages including 7 figures and 2 table.