MDE 10 End of Unit Quiz

A) Increases oil viscosity and reduces lubrication efficiency: Incorrect. Fuel dilution generally reduces oil viscosity and lubrication efficiency.

B) Reduces the oil’s ability to carry away heat: Incorrect. Fuel dilution affects lubrication and may not significantly impact heat dissipation.

C) Leads to increased oil consumption and potential for engine damage: Correct. Fuel dilution lowers the oil’s lubricating properties and can lead to increased oil consumption and engine wear.

D) Improves the oil’s cleaning ability: Incorrect. Fuel dilution actually reduces the oil's cleaning ability.

Explanation:

• A) A method where oil is forced under pressure between surfaces to create a lubricating film, eliminating metal-to-metal contact: Correct. Hydrostatic lubrication involves the use of a pressurized oil film to create a separation between surfaces, preventing metal-to-metal contact and reducing friction.
• B) A system where oil is distributed by gravity flow to lubricate moving parts in an engine: Incorrect. This describes a gravity-fed lubrication system, not hydrostatic lubrication.
• C) A technique that uses a splash of oil from rotating components to lubricate engine parts: Incorrect. This describes splash lubrication, not hydrostatic lubrication.
• D) A lubrication method where oil is sprayed onto components to reduce friction and wear: Incorrect. This describes spray lubrication, not hydrostatic lubrication.

Correct Answer: B) Total Base Number (TBN)

Explanation: The Total Base Number (TBN) measures the oil’s ability to neutralize acidic byproducts from combustion. A higher TBN indicates better capacity to protect engine parts from acid corrosion.

Correct Answers: A) Replace worn or damaged gears
C) Adjust or realign misaligned gears

Explanation:

• Replace worn or damaged gears: Worn or damaged gears can increase friction and cause operational issues. Replacing them with new gears addresses the root cause of the excessive friction.
• Adjust or realign misaligned gears: Misaligned gears can cause excessive friction and wear. Correcting the alignment ensures smooth engagement and operation of the gears, reducing friction.

Note: Increasing the gearbox oil temperature and decreasing the oil level are not effective solutions for dealing with friction issues due to worn or misaligned gears. Using a different type of lubricant might help in some cases but does not address the underlying mechanical issues with the gears themselves.

B) By a mechanical pump that circulates oil through the engine

Explanation: In forced circulation lubrication systems, a mechanical pump is used to circulate oil throughout the engine. This method ensures that oil reaches the cylinder liners and other critical areas consistently, which helps in maintaining proper lubrication and cooling.

B) Forced circulation lubrication

Explanation: Medium-speed diesel engines typically use forced circulation lubrication to ensure consistent oil delivery and effective cooling. This method is preferred over splash lubrication in these engines due to its ability to provide a more controlled and reliable oil supply.

Correct Answer: A) To ensure adequate cooling and prevent overheating of gearbox components

Explanation: Large quantities of lubricating oil in a gearbox are used primarily to ensure proper cooling and to prevent overheating of the gearbox components. The oil helps absorb and dissipate heat generated by the friction and mechanical work within the gearbox, maintaining operational efficiency and preventing damage.

Correct Answer: B) Keeping the oil free from moisture

Explanation: Keeping the oil free from moisture is essential in preventing oxidation. Moisture can accelerate the oxidation process, leading to the formation of acids and sludge that degrade the oil's quality.

Correct Answer: A) To prevent premature ignition and reduce fire risk

Explanation: A high flash point indicates that the oil can withstand higher temperatures before igniting, which is crucial in diesel engines where high temperatures are common. This helps in reducing the risk of fire and ensuring safety.

Explanation:

• A) Increased oil consumption: Excessive lubrication often results in higher oil consumption because surplus oil can leak or be burned off, leading to a need for more frequent topping up.
• B) Reduced friction: This is misleading. While lubrication does reduce friction, excessive lubrication does not necessarily lead to reduced friction; it can cause other issues such as oil foaming.
• C) Increased risk of oil foaming: Excessive lubrication can lead to oil foaming, which decreases the effectiveness of lubrication and can cause engine damage due to poor oil film formation.
• D) Enhanced cooling: This is incorrect. Excessive oil does not necessarily enhance cooling and can actually lead to problems such as oil foaming, which impairs the cooling function.

Correct Answer: C) Presence of water in the oil

Explanation: Microbial contamination often occurs when there is water present in the lubricating oil, as microbes thrive in the water-oil interface. This can lead to the formation of sludge and acids that degrade the oil and damage the engine.

Correct Answers: A) Presence of sludge in the oil
B) Unusual or foul odor from the oil
C) Increase in oil viscosity
D) Discoloration of the oil

Explanation: Microbial degradation of lubricating oil can cause the formation of sludge, an unpleasant odor, an increase in viscosity due to the by-products of microbial activity, and discoloration of the oil as it breaks down.