Diesel quality index: What is a typical cetane number value for diesel fuel used in heavy-duty trucks under normal specifications?

Introduction / Context:
Cetane number is the key ignition quality parameter for diesel fuels in compression-ignition engines. It indicates readiness of autoignition and affects cold starting, noise, and combustion smoothness in heavy-duty trucks and buses.

Given Data / Assumptions:

• On-road diesel specifications in many regions target cetane number around the high 40s to low 50s.
• Engines are designed to operate efficiently without excessive ignition delay at these values.
• Very low or very high cetane numbers are atypical for general truck diesel supply.

Concept / Approach:

A cetane number near 50 balances ignition quality, emissions, and refining economics. Too low a cetane causes long ignition delay and knock-like diesel knock; extremely high cetane is not commonly required and may reduce the natural mixing time that assists soot oxidation.

Step-by-Step Solution:

Verification / Alternative check:

Standards such as EN 590 and ASTM D975 require minimum cetane index or number often near 51 or 40–45 minimum depending on grade; practical supply for trucks often centers near 50.

Why Other Options Are Wrong:

14 / 35: Too low, would cause poor starting and harsh operation. 85: Not typical for commercial truck diesel; such high values are uncommon and unnecessary.

Common Pitfalls:

Confusing octane (gasoline) with cetane (diesel); assuming higher is always better regardless of engine design.

Final Answer:

50