Practice Test Geeks(CLS) Certified Lubrication Specialist Practice Test
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Lubrication Fundamentals & Applications Flashcards

7 cards from real CLS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. Which method of lubricant application delivers a fine mist of oil droplets entrained in an air stream to the point of lubrication?

    Answer: Oil mist lubrication

    Oil mist lubrication atomizes oil into micron-sized particles carried by compressed air to bearings and other components, providing a clean, minimal-quantity application.

  2. What is the primary function of a thickener in a lubricating grease?

    Answer: To act as a sponge that holds and releases base oil while providing structure

    The thickener (e.g., lithium soap, polyurea) forms a three-dimensional matrix that traps and releases base oil as needed while giving grease its semi-solid consistency.

  3. A gear oil is labeled 'ISO VG 220.' What does the '220' represent?

    Answer: The oil's kinematic viscosity in cSt at 40°C, midpoint of a defined range

    ISO VG 220 means the oil has a nominal kinematic viscosity of 220 cSt at 40°C, with the actual value falling within ±10% of that midpoint.

  4. What is 'fretting corrosion' and when does it typically occur?

    Answer: Surface damage from micro-slip oscillatory motion between closely fitted metal parts

    Fretting corrosion results from tiny oscillatory movements between press-fitted or clamped metal components, creating iron oxide debris and pitted, rough surfaces.

  5. Which base oil classification includes polyalphaolefins (PAOs)?

    Answer: API Group IV

    API Group IV base oils are fully synthetic polyalphaolefins, produced by oligomerization of alpha-olefins, offering superior VI, low pour point, and oxidation stability.

  6. What does the 'acid number' (AN) of a lubricant indicate?

    Answer: The amount of acidic components in the oil, measured by mg KOH/g needed to neutralize them

    Acid number (ASTM D974) measures total acidity in milligrams of KOH required per gram of oil, used to monitor lubricant degradation and additive depletion over time.

  7. In which lubrication application is a non-soap thickener like polyurea preferred over lithium complex grease?

    Answer: High-temperature electric motor bearings requiring long relubrication intervals

    Polyurea greases offer excellent high-temperature stability, oxidation resistance, and extended service life, making them ideal for sealed electric motor bearings.