Product colour, refinement, and quality indicators: Pick the statement that is incorrect regarding the colour and related qualitative cues of petroleum products.

Introduction / Context:
Colour is a simple visual attribute often recorded for petroleum products (e.g., ASTM colour). While it provides rough indications, engineers must avoid over-interpreting colour as a proxy for other properties like viscosity, which require direct measurement.

Given Data / Assumptions:

• Different products show characteristic colours based on refining and contaminant levels.
• Viscosity depends on molecular weight distribution and temperature, not just colour.
• Adulteration screening may use fluorescence or UV behaviour.

Concept / Approach:
Although lighter cuts are usually paler and also happen to have lower viscosity than heavy fuels, the inference “pale → low viscosity” is not a reliable rule for arbitrary samples. Additives, dyes, and contaminants can alter colour independently of viscosity. Thus, the categorical claim in option (a) is incorrect, whereas the other statements reflect cautious, qualified relationships.

Step-by-Step Solution:

Verification / Alternative check:
Product specifications for viscosity rely on kinematic viscosity tests (e.g., D445), independent of ASTM colour; standards treat colour as indicative only.

Why Other Options Are Wrong:

Common Pitfalls:
Treating visual colour as a surrogate for viscosity or performance; always confirm with standardized lab methods at controlled temperature.

Final Answer:
A pale colour of a petroleum product indicates lower viscosity.