🔍 Key Concepts

• Alkaline reserve (TBN – Total Base Number) and its role in neutralizing acids formed during fuel combustion • Differences in how trunk-type vs. crosshead diesel engines handle cylinder lubrication and crankcase oil • Which systems are exposed to acidic combustion products versus relatively clean working conditions

💭 Think About

• Which of these lubrication systems is most directly exposed to the byproducts of fuel combustion, especially sulfuric and other acids? • Why would an oil that can neutralize acids (has an alkaline reserve) be more important for some diesel engine designs than for turbines or bearings isolated from combustion gases? • In which engine type does the same oil both lubricate and help deal with contaminants from the combustion space?

✅ Before You Answer

• Identify which option involves oil that shares space with the combustion chamber or piston undercrown, not just clean bearings or gears • Confirm which engine design uses separate cylinder oil and crankcase oil, versus a common oil system • Eliminate any applications where the oil is not routinely contaminated by combustion acids (e.g., closed, clean systems)