Question 37 MODE01 - Chief MODU Engineer

The Correct Answer is D **Why option D ("The engine will crank slowly and may fail to start.") is correct:** Lube oil viscosity is highly dependent on temperature. When lube oil is excessively cold, its viscosity (thickness) increases dramatically. This extremely viscous oil resists flow and adds significant drag to all moving parts of the engine, including the crankshaft, connecting rods, and valve train. When the starter motor attempts to turn the engine over, it must overcome this increased mechanical resistance caused by the cold, thick oil. This results in the engine cranking very slowly, demanding much higher amperage from the batteries, and potentially failing to reach the minimum required speed for combustion (firing) to occur, leading to a failure to start. **Why the other options are incorrect:** * **A) The cooling system will overheat causing the engine to stall:** Excessively cold lube oil does not cause the cooling system to overheat. In fact, if the oil is too cold, the jacket water temperature is likely also low, and the immediate concern is high viscosity, not overheating. Overheating usually occurs due to a lack of coolant flow, high load, or high ambient temperature, not excessively cold oil. * **B) The engine will overspeed when started:** Overspeeding is typically caused by a runaway condition (e.g., ignition of external flammable vapor entering the air intake, or a fault in the governor/fuel rack system causing maximum fuel delivery). Excessively cold, high-viscosity oil creates massive resistance, which would make overspeeding virtually impossible during starting, and even difficult during normal operation. * **C) The fuel oil supply will become diluted resulting in rough running:** Fuel dilution of the lube oil (a phenomenon where fuel leaks into the oil) can cause rough running, but this is a chemical contamination issue, not a direct effect of the lube oil being too cold. Excessive coldness makes the oil thicker, not diluted. If the engine did manage to start, the rough running would be primarily due to increased friction and slow warm-up, not fuel dilution.