🔍 Key Concepts

• Cetane rating and how it relates to how easily diesel ignites under compression • Difference between ignition quality and energy content (calorific value) of a fuel • What flash point actually measures compared to combustion behavior in an engine

💭 Think About

• Think about what property is most important for diesel engines, which rely on compressing air and then injecting fuel without a spark plug. • Ask yourself: does cetane number describe how much energy is in the fuel, or how quickly/smoothly it starts burning when injected? • Consider which option refers to a lab test that measures how readily diesel starts combustion under specific conditions.

✅ Before You Answer

• Be clear on the difference between how easily fuel ignites vs how much heat it releases when burned. • Recall that flash point is about forming flammable vapors at low temperature, not about engine knock or start of combustion. • Eliminate any choices that describe how the engine uses the fuel (like consumption rate) rather than a tested fuel property.