Misfueling effect — petrol in a diesel engine: If petrol (gasoline) is used in a compression-ignition diesel engine, what is the most likely operational consequence?

Introduction / Context:
Diesel engines depend on auto-ignition of injected fuel in hot, highly compressed air. Petrol has a high octane rating (resists auto-ignition) and different volatility and lubricity characteristics. Using petrol in a diesel compromises injection system lubrication and alters ignition delay, often leading to harsh combustion phenomena.

Given Data / Assumptions:

• Compression-ignition engine with high compression ratio and in-cylinder temperatures.
• Petrol substituted for diesel in the fuel system (no adjustments).
• No knock-control electronics typical of SI engines.

Concept / Approach:
Petrol’s resistance to auto-ignition tends to lengthen ignition delay under diesel conditions. During this delay, more fuel can accumulate before combustion starts. When ignition finally occurs, a large fraction of premixed fuel-air burns almost simultaneously, causing a rapid pressure rise commonly perceived as severe knocking or “diesel knock.” Additionally, lack of lubricity in petrol can damage pumps/injectors and degrade spray quality, compounding abnormal combustion.

Step-by-Step Solution:

Verification / Alternative check:
Field experience and safety advisories warn against petrol contamination in diesel; symptoms include loud knocking, loss of power, hard starting, and potential injector-pump damage due to poor lubricity.

Why Other Options Are Wrong:

• Low power / low efficiency: These may also occur, but the most defining and immediate issue is the severe knock caused by altered ignition delay and heat release.
• Black smoke: Typically linked to rich, sooty combustion with heavy fuels; petrol contamination more often leads to misfire/knock and possible white or gray exhaust, not necessarily black smoke.

Common Pitfalls:
Assuming petrol will burn gently because it burns smoothly in SI engines; combustion phasing and initiation mechanisms are entirely different in CI engines.

Final Answer:
higher knocking will occur