CLS CLS Oil Analysis & Condition Monitoring 1 — Questions and Answers
Question 1: Which oil analysis test is primarily used to detect the presence of water contamination in a lubricant?
- Crackle test (Correct answer)
- Viscosity index measurement
- Acid number titration
- Flash point test
Correct answer: Crackle test
The crackle test involves placing a drop of oil on a hot plate; water contamination causes crackling or bubbling.
Question 2: What does a rising ferrous density (FD) value in an oil analysis report most likely indicate?
- Increased wear of ferrous metal components (Correct answer)
- Improved lubricant performance
- Decreased oil oxidation
- Lower contamination levels
Correct answer: Increased wear of ferrous metal components
Rising ferrous density indicates increasing iron particle concentration, signaling accelerated wear of steel or cast iron parts.
Question 3: The viscosity of an in-service lubricant has increased by 25% from its new-oil baseline. What is the most probable cause?
- Oxidation and thermal degradation (Correct answer)
- Water dilution
- Fuel dilution
- Coolant contamination
Correct answer: Oxidation and thermal degradation
Oxidation and thermal degradation form varnish and sludge precursors that significantly thicken the oil.
Question 4: Which elemental spectroscopy technique is most commonly used in oil analysis to identify wear metals?
- Inductively Coupled Plasma (ICP) (Correct answer)
- X-ray fluorescence (XRF) of bulk oil
- Atomic absorption spectroscopy of new oil
- Infrared spectroscopy
Correct answer: Inductively Coupled Plasma (ICP)
ICP spectroscopy accurately measures concentrations of wear metals, contaminants, and additive elements in parts per million.
Question 5: A Total Base Number (TBN) test on a diesel engine oil shows a value that has dropped to less than 50% of the new-oil TBN. What does this indicate?
- The oil's acid-neutralizing capacity is significantly depleted (Correct answer)
- The oil viscosity has improved
- The oil contains excess additives
- The oil is in excellent condition
Correct answer: The oil's acid-neutralizing capacity is significantly depleted
TBN measures the oil's ability to neutralize combustion acids; a drop below 50% signals the need for an oil change.
Question 6: In particle count analysis using ISO 4406, a code of 18/16/13 describes contamination levels for particles sized at which thresholds?
- ≥4 µm, ≥6 µm, ≥14 µm (Correct answer)
- ≥2 µm, ≥5 µm, ≥10 µm
- ≥5 µm, ≥10 µm, ≥20 µm
- ≥1 µm, ≥5 µm, ≥15 µm
Correct answer: ≥4 µm, ≥6 µm, ≥14 µm
ISO 4406:2021 reports particle counts per milliliter at ≥4 µm(c), ≥6 µm(c), and ≥14 µm(c) thresholds.
CLS CLS Oil Analysis & Condition Monitoring 1
Which oil analysis test is primarily used to detect the presence of water contamination in a lubricant?