Gasoline quality testing — which test is least significant? For motor gasoline, which of the following determinations is not generally considered a very significant routine test for product quality?

Introduction / Context:
Gasoline specifications focus on volatility, knock resistance, cleanliness, and emissions. Unlike diesel or lubricants, viscosity does not strongly affect carburetion or fuel injection at typical gasoline viscosities.

Given Data / Assumptions:

• Gasoline is a low-viscosity hydrocarbon blend.
• Key specs: octane number (anti-knock), RVP/volatility (starting and vapor lock), gum (deposits), sulfur (emissions).

Concept / Approach:
Viscosity differs only slightly among gasolines and does not materially impact engine operation within normal ranges. Therefore, it is not a primary routine control property compared to octane, RVP, gum, or sulfur.

Step-by-Step Solution:
Identify critical gasoline properties: octane, volatility (RVP), cleanliness (gum), and sulfur → all significant.Viscosity has minimal operational significance in SI engines for gasoline ranges → least significant.

Verification / Alternative check:
Standards (ASTM D4814) emphasize volatility and octane; viscosity is not a controlling parameter for motor gasoline.

Why Other Options Are Wrong:

• Gum and sulfur directly affect deposits and emissions.
• Octane number is central to performance and knock.
• RVP controls starting and vapor lock behavior.

Common Pitfalls:

• Assuming viscosity importance from diesel or lube practice; not applicable to gasoline in the same way.

Final Answer:
Viscosity