A 4-stroke diesel engine can be operated with either diesel (heating value 45 MJ kg^-1) or biodiesel blend, B20 (heating value 42.1 MJ kg^-1). The brake specific fuel consumption of the engine when operated with diesel and B20 is 260 g kW^-1 h^-1 and 310 g kW^-1 h^-1, respectively. For developing a brake power of 20 kW, the change in brake thermal efficiency of the engine when B20 is used in place of diesel is _______. (rounded off to 2 decimal places)