Industry practice reports pour point in standardized increments and defines it via a prescribed cooling/tilt procedure. Choose the correct statement about how pour point is expressed and defined.

Introduction / Context:
The pour point test determines the lowest temperature at which an oil will just flow under specified test conditions. Results are reported in discrete increments, with conventions differing between Celsius and Fahrenheit reporting.

Given Data / Assumptions:

• Standardized laboratory procedure (e.g., ASTM D97 or equivalent).
• Reporting may be in °C or °F depending on region.

Concept / Approach:
Under ASTM methods, pour point values are reported to the nearest 3°C increment (… , −12°C, −9°C, −6°C, −3°C, 0°C, 3°C, …). In Fahrenheit terms, this corresponds to increments of 5°F (… , 10°F, 5°F, 0°F, −5°F, −10°F, …). Therefore, saying “multiple of 3°F” is incorrect, while “multiple of 5°F” is correct. The definition is not “5°C below the temperature at which oil ceases to flow”; rather, it is the lowest temperature at which movement is observed under the test’s tilt protocol.

Step-by-Step Solution:

Verification / Alternative check:
Method descriptions and reporting guidelines show 3°C (≈5°F) increments; lab sheets round to these discrete values.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing reporting increments with cooling step sizes; follow the method’s specified rounding.

Final Answer:
Pour point is reported as a multiple of 5°F.