Question 26 QMED01 - Junior Engineer

The Correct Answer is D ### Why Option D ("Cylinder lubricating oil") is correct Cylinder lubricating oil is considered a consumable because, in a crosshead-type engine, it is injected directly onto the cylinder liner walls via timed lubricators. Its primary function is to lubricate the piston rings and liner, and to neutralize the corrosive sulfuric acids formed during the combustion of heavy fuel oil. Unlike the main system oil, the cylinder oil is **designed to be entirely used up** (burned during combustion or scraped down the liner) and is *not* recovered, filtered, and recirculated back into the supply tank. New oil must be continuously supplied to maintain lubrication and acid neutralization, making it a true operating consumable. *** ### Why the other options are incorrect **A) Piston cooling oil:** Piston cooling oil is generally supplied by the main circulating oil system. It is circulated through passages within the piston to remove heat, and then recovered back into the main engine sump (crankcase) where it is cooled and filtered for reuse. It is a circulating charge, not a consumable. **B) Turbocharger lubricating oil:** This oil lubricates the high-speed bearings of the turbocharger. Whether it is supplied by an independent system or tapped from the main engine system, it is always filtered, cooled, and recovered for continuous reuse. It is a circulating charge, not a consumable. **C) Main circulating oil:** The main circulating oil lubricates all the engine's running gear (bearings, crossheads, camshaft, etc.). It is stored in the main sump, constantly filtered, separated, cooled, and recirculated under pressure. Although there are minor losses (leakage, evaporation), the bulk of the oil charge is continuously reused and is therefore classified as a circulating charge, not a consumable.