When changing over from residual to distillate fuel on a slow-speed diesel main engine, what is a good guideline to follow regarding the change over?

Correct Answer: Option B — Rate of temperature change of fuel to the engine should not exceed 2 degrees C per minute.

Thermal shock prevention dictates limiting the fuel temperature change rate to a maximum of 2 degrees Celsius per minute during changeovers between hot residual fuel and cooler distillate fuel to protect precision fuel system components.