In a diesel engine lube oil cooler, with sea water cooling the lubricating oil, what statement is true?

Correct Answer: Option A — The lube oil pressure is always kept higher than the sea water pressure, and in case of a lube oil cooler leak, the lube oil sump level will decrease.

Lube oil system operating pressures exceed raw sea water cooling pressures to prevent sea water contamination of the oil. A cooler boundary failure forces high-pressure oil into the sea chest, directly resulting in a dropping sump level.